- Fix some errors, fix some performance warnings, and some simple (but effective) optimizations
- check for __GNUC__ instead of just assuming it
- Games.xml: Align ROM names with MAME.
- Minor and inconsequential change. Makes manual ROM building 'slightly'
- easier when using latest MAME ROM set (currently 0.245).
- slightly optimize DrawTileLine (less branches/logic)
- optimize ReadRegister, as localtime (at least on MSVC/Windows) is significantly showing up in profiling (e.g. in SW Trilogy)
- caches localtime until time changes (i.e. limits calls to 1/sec)
- use intrinsics for endian swap
- fix a real error (m68kdasm) and some harmless performance warnings and use modern headers
- fix some real errors (Model3,InputSystem), minor errors (SCSP,SDL/Main) an some performance warnings

- equivalent optimizations, NFC