[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.
ifeq ($(OS),osx)
LIBDYLIB=$(PLATFORM)/lib/.libs/$(LIBNAME).dylib
else ifeq ($(OS),ios)
LIBDYLIB=$(PLATFORM)/lib/.libs/$(LIBNAME).dylib
else
LIBDYLIB=$(PLATFORM)/lib/.libs/$(LIBNAME).so
endif

oh btw, shouldn't we use the opportunity and move texturepacker to depends?