Add preprocessor guard around CUTE_TILED_SNPRINTF

[mupfdev]

Some platforms do not provide that function. This way, the use of snprintf can be explicitly deactivated:

#define CUTE_TILED_SNPRINTF(ARGS...) (void)(ARGS)
#define CUTE_TILED_IMPLEMENTATION
#include <cute_tiled.h>

[mupfdev]

I wanted to create a separate pull request for the last commit. This obviously did not work. Instead, it was included here.

cute_tiled.h:176: redefinition of `cute_tiled_tileset_t'
cute_tiled.h:113: `cute_tiled_tileset_t' previously declared here

My compiler complained about a redefinition of cute_tiled_tileset_t. That is why I removed line 176. The definition must be known before line 143, that's why I didn't delete it in line 112.

[RandyGaul]

Thank you!