patch 8.0.1496: clearing a pointer takes two lines

Problem:    Clearing a pointer takes two lines.
Solution:   Add VIM_CLEAR() and replace vim_clear(). (Hirohito Higashi,
            closes #2629)
diff --git a/src/regexp.c b/src/regexp.c
index 7f5e265..d07391e 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -3996,10 +3996,7 @@
     /* Free "reg_tofree" when it's a bit big.
      * Free regstack and backpos if they are bigger than their initial size. */
     if (reg_tofreelen > 400)
-    {
-	vim_free(reg_tofree);
-	reg_tofree = NULL;
-    }
+	VIM_CLEAR(reg_tofree);
     if (regstack.ga_maxlen > REGSTACK_INITIAL)
 	ga_clear(&regstack);
     if (backpos.ga_maxlen > BACKPOS_INITIAL)
@@ -7521,8 +7518,7 @@
 	    {
 		STRCPY(dest, eval_result);
 		dst += STRLEN(eval_result);
-		vim_free(eval_result);
-		eval_result = NULL;
+		VIM_CLEAR(eval_result);
 	    }
 	}
 	else
@@ -8150,7 +8146,7 @@
      * First try the NFA engine, unless backtracking was requested.
      */
     if (regexp_engine != BACKTRACKING_ENGINE)
-        prog = nfa_regengine.regcomp(expr,
+	prog = nfa_regengine.regcomp(expr,
 		re_flags + (regexp_engine == AUTOMATIC_ENGINE ? RE_AUTO : 0));
     else
 	prog = bt_regengine.regcomp(expr, re_flags);
@@ -8170,7 +8166,7 @@
 	    }
 	    else
 		EMSG2("(NFA) Could not open \"%s\" to write !!!",
-                        BT_REGEXP_DEBUG_LOG_NAME);
+			BT_REGEXP_DEBUG_LOG_NAME);
 	}
 #endif
 	/*
@@ -8341,10 +8337,10 @@
     long
 vim_regexec_multi(
     regmmatch_T *rmp,
-    win_T       *win,           /* window in which to search or NULL */
-    buf_T       *buf,           /* buffer in which to search */
-    linenr_T    lnum,           /* nr of line to start looking for match */
-    colnr_T     col,            /* column to start looking for match */
+    win_T       *win,		/* window in which to search or NULL */
+    buf_T       *buf,		/* buffer in which to search */
+    linenr_T	lnum,		/* nr of line to start looking for match */
+    colnr_T	col,		/* column to start looking for match */
     proftime_T	*tm,		/* timeout limit or NULL */
     int		*timed_out)	/* flag is set when timeout limit reached */
 {