Hide third party header files from exported indielib headerfiles

[M-F-K]

User should NOT have to include third party header files / libraries in their compile setup.

This is currently a problem regarding the Spriter, TILED (TMX) and TrueType header files.

[M-F-K]

True type issue is probably fixed now, - have not got around to test it.

[M-F-K]

Spriter is not a problem,- so currently there is only TMX left ( the #include "dependencies/TmxParser/Tmx.h" in IND_TmxMap.h).