vim-patch:7.4.233

Problem:  Escaping special characters for using "%" with a shell command
          is inconsistant: parentheses are escaped but spaces are not.

Solution: Only escape "!". (Gary Johnson)

https://code.google.com/p/vim/source/detail?r=22a1d5762ba3a75984e89dcc47a65498f63a6c2c