src: fix build on MSVC
src: fix build on MSVC

Do explicit casts from/to enums, convert type of `memchr`'s return value
to `const char*`.

PR-URL: https://github.com/joyent/http-parser/pull/213
Reviewed-By: Bert Belder <9f2ff180696da386c1be31b4507155616db25dc6@gmail.com>

OpenMusicKontrollers/chimaerad,OpenMusicKontrollers/chimaerad,OpenMusicKontrollers/chimaerad,OpenMusicKontrollers/chimaerad,OpenMusicKontrollers/chimaerad,OpenMusicKontrollers/chimaerad