patch 9.0.1168: code to enable/disable mouse is not from terminfo/termcap

Problem:    Code to enable/disable mouse is not from terminfo/termcap.
Solution:   Request the "XM" entry and use it to set 'ttymouse' if possible.
diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index a514b6f..0fc00b4 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -8679,6 +8679,9 @@
 	set to a name that starts with "xterm", "mlterm", "screen", "tmux",
 	"st" (full match only), "st-" or "stterm", and 'ttymouse' is not set
 	already.
+	If the terminfo/termcap entry "XM" exists and the first number is
+	"1006" then 'ttymouse' will be set to "sgr".  This works for many
+	modern terminals.
 	Additionally, if vim is compiled with the |+termresponse| feature and
 	|t_RV| is set to the escape sequence to request the xterm version
 	number, more intelligent detection is done.
diff --git a/src/optiondefs.h b/src/optiondefs.h
index de9fb6a..4d12e25 100644
--- a/src/optiondefs.h
+++ b/src/optiondefs.h
@@ -2934,6 +2934,7 @@
     p_term("t_vs", T_VS)
     p_term("t_WP", T_CWP)
     p_term("t_WS", T_CWS)
+    p_term("t_XM", T_CXM)
     p_term("t_xn", T_XN)
     p_term("t_xs", T_XS)
     p_term("t_ZH", T_CZH)
diff --git a/src/os_unix.c b/src/os_unix.c
index 9d8d466..194f4be 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -3780,7 +3780,11 @@
     }
 #endif
 
-    if (ttym_flags == TTYM_SGR)
+    if (T_CXM != NULL && *T_CXM != NUL)
+    {
+	term_enable_mouse(on);
+    }
+    else if (ttym_flags == TTYM_SGR)
     {
 	// SGR mode supports columns above 223
 	out_str_nf((char_u *)(on ? "\033[?1006h" : "\033[?1006l"));
diff --git a/src/proto/term.pro b/src/proto/term.pro
index 8c8b813..4c93a81 100644
--- a/src/proto/term.pro
+++ b/src/proto/term.pro
@@ -25,6 +25,7 @@
 void term_cursor_right(int i);
 void term_append_lines(int line_count);
 void term_delete_lines(int line_count);
+void term_enable_mouse(int enable);
 void term_set_winpos(int x, int y);
 int term_get_winpos(int *x, int *y, varnumber_T timeout);
 void term_set_winsize(int height, int width);
diff --git a/src/term.c b/src/term.c
index 0bb6d71..43d0db6 100644
--- a/src/term.c
+++ b/src/term.c
@@ -473,6 +473,7 @@
     {(int)KS_CGP,	"\033[13t"},
 #  endif
     {(int)KS_CRV,	"\033[>c"},
+    {(int)KS_CXM,	"\033[?1006;1000%?%p1%{1}%=%th%el%;"},
     {(int)KS_RFG,	"\033]10;?\007"},
     {(int)KS_RBG,	"\033]11;?\007"},
     {(int)KS_U7,	"\033[6n"},
@@ -1229,6 +1230,7 @@
     {(int)KS_CWP,	"[%dCWP%d]"},
 #  endif
     {(int)KS_CRV,	"[CRV]"},
+    {(int)KS_CXM,	"[CXM]"},
     {(int)KS_U7,	"[U7]"},
     {(int)KS_RFG,	"[RFG]"},
     {(int)KS_RBG,	"[RBG]"},
@@ -1721,7 +1723,8 @@
 			{KS_BC, "bc"}, {KS_CSB,"Sb"}, {KS_CSF,"Sf"},
 			{KS_CAB,"AB"}, {KS_CAF,"AF"}, {KS_CAU,"AU"},
 			{KS_LE, "le"},
-			{KS_ND, "nd"}, {KS_OP, "op"}, {KS_CRV, "RV"},
+			{KS_ND, "nd"}, {KS_OP, "op"},
+			{KS_CRV, "RV"}, {KS_CXM, "XM"},
 			{KS_VS, "vs"}, {KS_CVS, "VS"},
 			{KS_CIS, "IS"}, {KS_CIE, "IE"},
 			{KS_CSC, "SC"}, {KS_CEC, "EC"},
@@ -2107,8 +2110,8 @@
     else
 	T_CCS = empty_option;
 
-    // Special case: "kitty" does not normally have a "RV" entry in terminfo,
-    // but we need to request the version for several other things to work.
+    // Special case: "kitty" may not have a "RV" entry in terminfo, but we need
+    // to request the version for several other things to work.
     if (strstr((char *)term, "kitty") != NULL
 					   && (T_CRV == NULL || *T_CRV == NUL))
 	T_CRV = (char_u *)"\033[>c";
@@ -2156,6 +2159,22 @@
     init_term_props(FALSE);
 #endif
 
+    // If the first number in t_XM is 1006 then the terminal will support SGR
+    // mouse reporting.
+    int did_set_ttym = FALSE;
+    if (T_CXM != NULL && *T_CXM != NUL && !option_was_set((char_u *)"ttym"))
+    {
+	char_u *p = T_CXM;
+
+	while (*p != NUL && !VIM_ISDIGIT(*p))
+	    ++p;
+	if (getdigits(&p) == 1006)
+	{
+	    did_set_ttym = TRUE;
+	    set_option_value_give_err((char_u *)"ttym", 0L, (char_u *)"sgr", 0);
+	}
+    }
+
 #if defined(UNIX) || defined(VMS)
     /*
      * For Unix, set the 'ttymouse' option to the type of mouse to be used.
@@ -2173,7 +2192,7 @@
 		p = (char_u *)"xterm";
 	}
 # endif
-	if (p != NULL)
+	if (p != NULL && !did_set_ttym)
 	{
 	    set_option_value_give_err((char_u *)"ttym", 0L, p, 0);
 	    // Reset the WAS_SET flag, 'ttymouse' can be set to "sgr" or
@@ -2801,8 +2820,8 @@
     if (out_pos > OUT_SIZE - MAX_ESC_SEQ_LEN)
 	out_flush();
 
-    while (*s)
-	out_char_nf(*s++);
+    for (char_u *p = s; *p != NUL; ++p)
+	out_char_nf(*p);
 
     // For testing we write one string at a time.
     if (p_wd)
@@ -2942,6 +2961,15 @@
     OUT_STR(tgoto((char *)T_CDL, 0, line_count));
 }
 
+#if defined(UNIX) || defined(PROTO)
+    void
+term_enable_mouse(int enable)
+{
+    int on = enable ? 1 : 0;
+    OUT_STR(tgoto((char *)T_CXM, 0, on));
+}
+#endif
+
 #if defined(HAVE_TGETENT) || defined(PROTO)
     void
 term_set_winpos(int x, int y)
diff --git a/src/termdefs.h b/src/termdefs.h
index a258dad..0239965 100644
--- a/src/termdefs.h
+++ b/src/termdefs.h
@@ -95,6 +95,7 @@
     KS_CGP,	// get window position
     KS_CWS,	// set window size in characters
     KS_CRV,	// request version string
+    KS_CXM,	// enable/disable mouse reporting
     KS_RFG,	// request foreground color
     KS_RBG,	// request background color
     KS_CSI,	// start insert mode (bar cursor)
@@ -205,6 +206,7 @@
 #define T_CEI	(TERM_STR(KS_CEI))	// end insert mode
 #define T_CSR	(TERM_STR(KS_CSR))	// start replace mode
 #define T_CRV	(TERM_STR(KS_CRV))	// request version string
+#define T_CXM	(TERM_STR(KS_CXM))	// enable/disable mouse reporting
 #define T_RFG	(TERM_STR(KS_RFG))	// request foreground RGB
 #define T_RBG	(TERM_STR(KS_RBG))	// request background RGB
 #define T_OP	(TERM_STR(KS_OP))	// original color pair
diff --git a/src/version.c b/src/version.c
index a218a71..56cbdd4 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1168,
+/**/
     1167,
 /**/
     1166,