patch 8.0.1346: crash when passing 50 char string to balloon_split()

Problem:    Crash when passing 50 char string to balloon_split().
Solution:   Fix off-by-one error.

Author: brammool

src/popupmnu.c

@@ -836,7 +836,7 @@ split_message(char_u *mesg, pumitem_T **array)
 	item->bytelen = p - item->start;
 	if (item->cells > max_cells)
 	    max_cells = item->cells;
-	long_item_count += item->cells / BALLOON_MIN_WIDTH;
+	long_item_count += (item->cells - 1) / BALLOON_MIN_WIDTH;
     }
 
     height = 2 + ga.ga_len;

src/testdir/test_popup.vim

@@ -707,6 +707,10 @@ func Test_balloon_split()
   if !exists('*balloon_split')
     return
   endif
+  call assert_equal([
+        \ 'tempname: 0x555555e380a0 "/home/mool/.viminfz.tmp"',
+        \ ], balloon_split(
+        \ 'tempname: 0x555555e380a0 "/home/mool/.viminfz.tmp"'))
   call assert_equal([
         \ 'one two three four one two three four one two thre',
         \ 'e four',

src/version.c

@@ -771,6 +771,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1346,
 /**/
     1345,
 /**/