[RFC] vim-patch:7.4.204

Merging vim-patch:7.4.204

Problem:    A mapping where the second byte is 0x80 doesn't work.
Solution:   Unescape before checking for incomplete multi-byte char. (Nobuhiro
            Takasaki)

https://code.google.com/p/vim/source/detail?r=f5120cbf16b9a9c6e0fbb599a6524e05ecf11393