[RFC] vim-patch:7.4.191

Merging vim-patch:7.4.191
Runtime files were already updated in https://github.com/neovim/docs/pull/3.


Problem:    Escaping a file name for shell commands can't be done without a
            function.
Solution:   Add the :S file name modifier.

https://code.google.com/p/vim/source/detail?r=40f18a1c1592c8b4047f6f2a413557f48a99c55f