patch 9.1.0309: crash when 'textwidth' > MAX_INT

Problem:  crash when 'textwidth' > MAX_INT (after vv9.1.0055)
          (Zoltan Balogh)
Solution: limit textwidth to MAX_INT

fixes: #14482
closes: #14489

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/textformat.c b/src/textformat.c
index 14acc53..41ec2cf 100644
--- a/src/textformat.c
+++ b/src/textformat.c
@@ -56,6 +56,7 @@
     colnr_T	leader_len;
     int		no_leader = FALSE;
     int		do_comments = (flags & INSCHAR_DO_COM);
+    int		safe_tw = trim_to_int(8 * (vimlong_T)textwidth);
 #ifdef FEAT_LINEBREAK
     int		has_lbr = curwin->w_p_lbr;
 
@@ -95,7 +96,7 @@
 	// Cursor is currently at the end of line. No need to format
 	// if line length is less than textwidth (8 * textwidth for
 	// utf safety)
-	if (curwin->w_cursor.col < 8 * textwidth)
+	if (curwin->w_cursor.col < safe_tw)
 	{
 	    virtcol = get_nolist_virtcol()
 		+ char2cells(c != NUL ? c : gchar_cursor());
@@ -156,8 +157,7 @@
 	// line to textwidth border every time for each line break.
 	//
 	// Ceil to 8 * textwidth to optimize.
-	curwin->w_cursor.col = startcol < 8 * textwidth ? startcol :
-	    8 * textwidth;
+	curwin->w_cursor.col = startcol < safe_tw ? startcol : safe_tw;
 
 	foundcol = 0;
 	skip_pos = 0;