When using image compression on PowerPC architecture, colors are in
wrong order ARGB -> BGRA.
This commit introduces macros, that will change the color order
according to machine endianness.
Theese macros are similar to QEMU macros in qemu-pixman.h
Since some spice C++ code is using code from common/, the C
functions need to be marked as such for the C++ compiler, otherwise
we'll get linkage issues.
This includes:
* pixman region from SpiceRects
* rop2 enum
* solid fill
* solid fill with rop
* tiled fill
* tiled fill with rop
* blit
* blit with rop
* copy rect