revert #652

reverting broad cosmetic/style change because:
- increases merge-conflicts
- increases overhead of merging upstream Vim patches
- reasons for change are ambiguous, so default to no change

src/ui.c

@@ -1075,7 +1075,7 @@ int vcol2col(win_T *wp, linenr_T lnum, int vcol)
   char_u      *start;
 
   start = ptr = ml_get_buf(wp->w_buffer, lnum, FALSE);
-  while (count < vcol && *ptr != '\0') {
+  while (count < vcol && *ptr != NUL) {
     count += win_lbr_chartabsize(wp, ptr, count, NULL);
     mb_ptr_adv(ptr);
   }