[WIP] vim-patch:7.4.324

Problem:   In Ex mode, cyrillic characters are not handled. (Stas Malavin)
Solution:   Support multi-byte characters in Ex mode. (Yukihiro Nakadaira)

https://code.google.com/p/vim/source/detail?r=c476e0ac8b406693c3877baffa0e97ff25e59b06

- I have changed one prefix ++ operator to postfix.
- I'm not sure about the formatting of the ifdefs, maybe some adjustments will be needed there
- Does anyone know how to test this patch? Maybe there is someone on the Neovim team who uses Cyrillic characters.
At this point I am not sure that we always have at least one free byte at the end of `line_ga.ga_data`:

If the code after `add_indent:` was executed, we could end up with `line_ga.maxlen == line_ga.ga_len` 
(if we added `line_ga.maxlen - line_ga.ga_len` spaces). 

So `p[line_ga.ga_len] = NUL` would be a buffer overrun.