Since these functions are now specific to paths and shouldn't be used on arbitrary string buffers (since they don't take a length), I wonder if they should be renamed `git_win32_path_utf8_to_16` and `git_win32_path_utf16_to_8`. Thanks a little awkward for my taste, so probably not, but I thought I'd throw it out there to see what you think.

One related thought is to make `git__utf8_to_16()` and `git__utf16_to_8()` actually take a length parameter (i.e. make the consistent by having both take a length and not assume `GIT_WIN_PATH_...`) and then create `GIT_INLINE(int) git_win32_path_utf8_to_16(...)` and vice versa that call the generic versions with the known length. Then the couple of places that use `git__utf8_to_16` on non-`GIT_WIN_PATH` buffers could just stay as they are, and the majority would be converted to use the path versions.