Missing `#include <cstdint>` in freetypelib.h?

Really not a big deal but I had to add that `#include` in order to avoid a compilation error. In my experience, what's provided by system header files varies between compiler versions, and since `uint32_t` is used in the freetypelib.h, maybe the source code is not compliant with the C++ standard without that `#include`.

Other than that, works like charm on my Ubuntu machine. Beautiful! Thanks.