patch 8.1.1901: the +insert_expand feature is not always available

Problem:    The +insert_expand feature is not always available.
Solution:   Graduate the +insert_expand feature.
diff --git a/src/option.c b/src/option.c
index 8d9b578..b625587 100644
--- a/src/option.c
+++ b/src/option.c
@@ -83,11 +83,9 @@
 #ifdef FEAT_COMMENTS
 # define PV_COM		OPT_BUF(BV_COM)
 #endif
-#ifdef FEAT_INS_EXPAND
-# define PV_CPT		OPT_BUF(BV_CPT)
-# define PV_DICT	OPT_BOTH(OPT_BUF(BV_DICT))
-# define PV_TSR		OPT_BOTH(OPT_BUF(BV_TSR))
-#endif
+#define PV_CPT		OPT_BUF(BV_CPT)
+#define PV_DICT	OPT_BOTH(OPT_BUF(BV_DICT))
+#define PV_TSR		OPT_BOTH(OPT_BUF(BV_TSR))
 #define PV_CSL		OPT_BUF(BV_CSL)
 #ifdef FEAT_COMPL_FUNC
 # define PV_CFU		OPT_BUF(BV_CFU)
@@ -301,9 +299,7 @@
 #ifdef FEAT_FOLDING
 static char_u	*p_cms;
 #endif
-#ifdef FEAT_INS_EXPAND
 static char_u	*p_cpt;
-#endif
 #ifdef FEAT_COMPL_FUNC
 static char_u	*p_cfu;
 static char_u	*p_ofu;
@@ -850,13 +846,8 @@
 			    (char_u *)&p_cp, PV_NONE,
 			    {(char_u *)TRUE, (char_u *)FALSE} SCTX_INIT},
     {"complete",    "cpt",  P_STRING|P_ALLOCED|P_VI_DEF|P_ONECOMMA|P_NODUP,
-#ifdef FEAT_INS_EXPAND
 			    (char_u *)&p_cpt, PV_CPT,
 			    {(char_u *)".,w,b,u,t,i", (char_u *)0L}
-#else
-			    (char_u *)NULL, PV_NONE,
-			    {(char_u *)0L, (char_u *)0L}
-#endif
 			    SCTX_INIT},
     {"concealcursor","cocu", P_STRING|P_ALLOCED|P_RWIN|P_VI_DEF,
 #ifdef FEAT_CONCEAL
@@ -885,13 +876,8 @@
 #endif
 			    SCTX_INIT},
     {"completeopt",   "cot",  P_STRING|P_VI_DEF|P_ONECOMMA|P_NODUP,
-#ifdef FEAT_INS_EXPAND
 			    (char_u *)&p_cot, PV_NONE,
 			    {(char_u *)"menu,preview", (char_u *)0L}
-#else
-			    (char_u *)NULL, PV_NONE,
-			    {(char_u *)0L, (char_u *)0L}
-#endif
 			    SCTX_INIT},
     {"completepopup", "cpp", P_STRING|P_VI_DEF|P_COMMA|P_NODUP,
 #if defined(FEAT_TEXT_PROP) && defined(FEAT_QUICKFIX)
@@ -903,7 +889,7 @@
 #endif
 			    SCTX_INIT},
     {"completeslash",   "csl",  P_STRING|P_VI_DEF|P_VIM,
-#if defined(FEAT_INS_EXPAND) && defined(BACKSLASH_IN_FILENAME)
+#if defined(BACKSLASH_IN_FILENAME)
 			    (char_u *)&p_csl, PV_CSL,
 			    {(char_u *)"", (char_u *)0L}
 #else
@@ -1023,11 +1009,7 @@
 			    (char_u *)&p_deco, PV_NONE,
 			    {(char_u *)FALSE, (char_u *)0L} SCTX_INIT},
     {"dictionary",  "dict", P_STRING|P_EXPAND|P_VI_DEF|P_ONECOMMA|P_NODUP|P_NDNAME,
-#ifdef FEAT_INS_EXPAND
 			    (char_u *)&p_dict, PV_DICT,
-#else
-			    (char_u *)NULL, PV_NONE,
-#endif
 			    {(char_u *)"", (char_u *)0L} SCTX_INIT},
     {"diff",	    NULL,   P_BOOL|P_VI_DEF|P_RWIN|P_NOGLOB,
 #ifdef FEAT_DIFF
@@ -2198,18 +2180,10 @@
 			    (char_u *)&p_prompt, PV_NONE,
 			    {(char_u *)TRUE, (char_u *)0L} SCTX_INIT},
     {"pumheight",   "ph",   P_NUM|P_VI_DEF,
-#ifdef FEAT_INS_EXPAND
 			    (char_u *)&p_ph, PV_NONE,
-#else
-			    (char_u *)NULL, PV_NONE,
-#endif
 			    {(char_u *)0L, (char_u *)0L} SCTX_INIT},
     {"pumwidth",    "pw",   P_NUM|P_VI_DEF,
-#ifdef FEAT_INS_EXPAND
 			    (char_u *)&p_pw, PV_NONE,
-#else
-			    (char_u *)NULL, PV_NONE,
-#endif
 			    {(char_u *)15L, (char_u *)15L} SCTX_INIT},
     {"pythonthreedll",  NULL,   P_STRING|P_EXPAND|P_VI_DEF|P_SECURE,
 #if defined(DYNAMIC_PYTHON3)
@@ -2796,11 +2770,7 @@
 			    (char_u *)&p_tw, PV_TW,
 			    {(char_u *)0L, (char_u *)0L} SCTX_INIT},
     {"thesaurus",   "tsr",  P_STRING|P_EXPAND|P_VI_DEF|P_ONECOMMA|P_NODUP|P_NDNAME,
-#ifdef FEAT_INS_EXPAND
 			    (char_u *)&p_tsr, PV_TSR,
-#else
-			    (char_u *)NULL, PV_NONE,
-#endif
 			    {(char_u *)"", (char_u *)0L} SCTX_INIT},
     {"tildeop",	    "top",  P_BOOL|P_VI_DEF|P_VIM,
 			    (char_u *)&p_to, PV_NONE,
@@ -3248,11 +3218,9 @@
 				NULL};
 static char *(p_fcl_values[]) = {"all", NULL};
 #endif
-#ifdef FEAT_INS_EXPAND
 static char *(p_cot_values[]) = {"menu", "menuone", "longest", "preview", "popup", "noinsert", "noselect", NULL};
-# ifdef BACKSLASH_IN_FILENAME
+#ifdef BACKSLASH_IN_FILENAME
 static char *(p_csl_values[]) = {"slash", "backslash", NULL};
-# endif
 #endif
 #ifdef FEAT_SIGNS
 static char *(p_scl_values[]) = {"yes", "no", "auto", "number", NULL};
@@ -5794,9 +5762,7 @@
 #if defined(FEAT_SMARTINDENT) || defined(FEAT_CINDENT)
     check_string_option(&buf->b_p_cinw);
 #endif
-#ifdef FEAT_INS_EXPAND
     check_string_option(&buf->b_p_cpt);
-#endif
 #ifdef FEAT_COMPL_FUNC
     check_string_option(&buf->b_p_cfu);
     check_string_option(&buf->b_p_ofu);
@@ -5816,10 +5782,8 @@
     check_string_option(&buf->b_p_path);
     check_string_option(&buf->b_p_tags);
     check_string_option(&buf->b_p_tc);
-#ifdef FEAT_INS_EXPAND
     check_string_option(&buf->b_p_dict);
     check_string_option(&buf->b_p_tsr);
-#endif
 #ifdef FEAT_LISP
     check_string_option(&buf->b_p_lw);
 #endif
@@ -7381,7 +7345,6 @@
     }
 #endif
 
-#ifdef FEAT_INS_EXPAND
     /* check if it is a valid value for 'complete' -- Acevedo */
     else if (gvarp == &p_cpt)
     {
@@ -7434,7 +7397,7 @@
 	    completeopt_was_set();
     }
 
-# ifdef BACKSLASH_IN_FILENAME
+#ifdef BACKSLASH_IN_FILENAME
     // 'completeslash'
     else if (gvarp == &p_csl)
     {
@@ -7442,8 +7405,7 @@
 		|| check_opt_strings(curbuf->b_p_csl, p_csl_values, FALSE) != OK)
 	    errmsg = e_invarg;
     }
-# endif
-#endif // FEAT_INS_EXPAND
+#endif
 
 #ifdef FEAT_SIGNS
     // 'signcolumn'
@@ -10959,14 +10921,12 @@
 	    clear_string_option(&buf->b_p_inc);
 	    break;
 #endif
-#ifdef FEAT_INS_EXPAND
 	case PV_DICT:
 	    clear_string_option(&buf->b_p_dict);
 	    break;
 	case PV_TSR:
 	    clear_string_option(&buf->b_p_tsr);
 	    break;
-#endif
 	case PV_FP:
 	    clear_string_option(&buf->b_p_fp);
 	    break;
@@ -11045,10 +11005,8 @@
 	    case PV_DEF:  return (char_u *)&(curbuf->b_p_def);
 	    case PV_INC:  return (char_u *)&(curbuf->b_p_inc);
 #endif
-#ifdef FEAT_INS_EXPAND
 	    case PV_DICT: return (char_u *)&(curbuf->b_p_dict);
 	    case PV_TSR:  return (char_u *)&(curbuf->b_p_tsr);
-#endif
 #if defined(FEAT_BEVAL) && defined(FEAT_EVAL)
 	    case PV_BEXPR: return (char_u *)&(curbuf->b_p_bexpr);
 #endif
@@ -11109,12 +11067,10 @@
 	case PV_INC:	return *curbuf->b_p_inc != NUL
 				    ? (char_u *)&(curbuf->b_p_inc) : p->var;
 #endif
-#ifdef FEAT_INS_EXPAND
 	case PV_DICT:	return *curbuf->b_p_dict != NUL
 				    ? (char_u *)&(curbuf->b_p_dict) : p->var;
 	case PV_TSR:	return *curbuf->b_p_tsr != NUL
 				    ? (char_u *)&(curbuf->b_p_tsr) : p->var;
-#endif
 	case PV_FP:	return *curbuf->b_p_fp != NUL
 				    ? (char_u *)&(curbuf->b_p_fp) : p->var;
 #ifdef FEAT_QUICKFIX
@@ -11229,11 +11185,9 @@
 #ifdef FEAT_FOLDING
 	case PV_CMS:	return (char_u *)&(curbuf->b_p_cms);
 #endif
-#ifdef FEAT_INS_EXPAND
 	case PV_CPT:	return (char_u *)&(curbuf->b_p_cpt);
-# ifdef BACKSLASH_IN_FILENAME
+#ifdef BACKSLASH_IN_FILENAME
 	case PV_CSL:	return (char_u *)&(curbuf->b_p_csl);
-# endif
 #endif
 #ifdef FEAT_COMPL_FUNC
 	case PV_CFU:	return (char_u *)&(curbuf->b_p_cfu);
@@ -11626,11 +11580,9 @@
 	    buf->b_p_ml_nobin = p_ml_nobin;
 	    buf->b_p_inf = p_inf;
 	    buf->b_p_swf = cmdmod.noswapfile ? FALSE : p_swf;
-#ifdef FEAT_INS_EXPAND
 	    buf->b_p_cpt = vim_strsave(p_cpt);
-# ifdef BACKSLASH_IN_FILENAME
+#ifdef BACKSLASH_IN_FILENAME
 	    buf->b_p_csl = vim_strsave(p_csl);
-# endif
 #endif
 #ifdef FEAT_COMPL_FUNC
 	    buf->b_p_cfu = vim_strsave(p_cfu);
@@ -11741,10 +11693,8 @@
 	    buf->b_p_inex = vim_strsave(p_inex);
 # endif
 #endif
-#ifdef FEAT_INS_EXPAND
 	    buf->b_p_dict = empty_option;
 	    buf->b_p_tsr = empty_option;
-#endif
 #ifdef FEAT_TEXTOBJ
 	    buf->b_p_qe = vim_strsave(p_qe);
 #endif