[Texturepacker] - removesdl

This removes SDL from TexturePacker and replaces its functionality in favor of an imagedecoder abstraction with with implementations for libgif, libpng and libjpeg. This is a followup of the last devcon discussion for the goal to remove SDL (which might be a bit liquid now).

@davilla here it is ...

It also fixes the completly broken win32 projects files and removes MakeDDS because it wasn't used @MartijnKaijser  @ronie - correct me if MakeDDS was used by some then i will try to fix it - but its a pita.
@wsnipex it builds both but there was another bug in there because the libname (e.x. tarball name) is giflib but the libname is libgif ... so i changed it to check for libgif.a.