redraw before echo

Redraw before echoing a progress message.

Fixes fatih#1732

Author: bhcleek

autoload/go/util.vim

@@ -313,6 +313,7 @@ function! s:echo(msg, hi)
   " Tabs display as ^I or <09>, so manually expand them.
   let l:msg = map(l:msg, 'substitute(v:val, "\t", "        ", "")')
 
+  redraw
   exe 'echohl ' . a:hi
   for line in l:msg
     echom "vim-go: " . line