Add a lisp function call replacement

Not sure how useful this is but we'll sneak it in undocumented.

plugin/surround.vim

@@ -224,6 +224,10 @@ function! s:wrap(string,char,type,...)
         let after = ' ' . after
       endif
     endif
+  elseif newchar ==# "\<C-F>"
+    let fnc = input('function: ')
+    let before = '('.fnc.' '
+    let after = ')'
   elseif idx >= 0
     let spc = (idx % 3) == 1 ? " " : ""
     let idx = idx / 3 * 3