move getwinvar over

autoload/airline/util.vim

@@ -1,6 +1,12 @@
 " MIT license. Copyright (c) 2013 Bailey Ling.
 " vim: ts=2 sts=2 sw=2 fdm=indent
 
+" for 7.2 compatibility
+function! airline#util#getwinvar(winnr, key, ...)
+  let winvals = getwinvar(a:winnr, '')
+  return get(winvals, a:key, (a:0 ? a:1 : ''))
+endfunction
+
 function! airline#util#exec_funcrefs(list, break_early)
   " for 7.2; we cannot iterate list, hence why we use range()
   " for 7.3-[97, 328]; we cannot reuse the variable, hence the {}