patch 8.1.0611: crash when using terminal with long composing characters

Problem:    Crash when using terminal with long composing characters.
Solution:   Make space for all characters. (Yasuhiro Matsumoto, closes #3619,
            closes #3703)

Author: brammool

src/terminal.c

@@ -1561,7 +1561,8 @@ update_snapshot(term_T *term)
 
 			cell2cellattr(&cell, &p[pos.col]);
 
-			if (ga_grow(&ga, MB_MAXBYTES) == OK)
+			// Each character can be up to 6 bytes.
+			if (ga_grow(&ga, VTERM_MAX_CHARS_PER_CELL * 6) == OK)
 			{
 			    int	    i;
 			    int	    c;

src/version.c

@@ -799,6 +799,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    611,
 /**/
     610,
 /**/