fix: trigger fold recomputation by querying foldlevel

Problem:
* Redrawing may break some plugins. For example, evaluating statusline
  may use to buffer variables that are initialized in some autocommands.
  But FastFold's autocmds may run before than them. So redrawing may
  result in using some undefined variable.
* Redrawing makes the screen flash.

Solution:
Querying foldlevel seems to be sufficient for triggerring fold
recomputation.

Author: tomtomjhj

plugin/fastfold.vim

@@ -72,10 +72,9 @@ endfunction
 if exists('*win_execute')
   function! s:WinDo( command )
     for w in range(1, winnr('$'))
-      call win_execute(win_getid(w), a:command, 1)
+      " query foldlevel to trigger recomputation of folds
+      call win_execute(win_getid(w), a:command . ' | call foldlevel(1)', 1)
     endfor
-    " trigger recomputation of fold
-    redraw
   endfunction
 else
   " See http://vim.wikia.com/wiki/Run_a_command_in_multiple_buffers#Restoring_position