Include stdint.h instead of inttypes.h in libmumblelink.c

MSVC 2010 has stdint.h but not inttypes.h.
Debian (GCC, MinGW) and OS X (Clang) can compile using stdint.h.
Make travis do all the builds again

Travis was only using the last env section, not merged them and was only doing
one build using gcc instead of six builds (gcc, clang, mingw, ..).