SDL_TTF and freetype not building with PTHREADS

If using SDL2 with threads then sdl2_ttf.py and freetype.py don't compile a -mt version of the library automatically like sdl2.py does.

We found that the linker dosnt seem to complain about linking the non-mt versionf of these librarys, but when using TTF_OpenFont you get heap corruption at runtime.

I changed sdl2.ttf.py and freetype to compile with USE_PTHREADS, linked with those library's and it fixed the heap corruption.