Drop C99 mode for better merging with CommandT upstream and mingw support
Merge CommandT upstream fix for memoization

See wincent/Command-T@26fca4c4076386f51f1d6f1881d17e279b1ab84c
See wincent/Command-T@94bd7d0806bdc60d42b14dbfa770decdaa257494
Rename C functions to avoid conflicts with CommandT

Fixes #15