[Scummvm-devel] Two new OSystem methods

[Max Horn]

FYI, dear porters, there are two new OSystem methods as of now:

* grabRawScreen (optional):
   returns the (8bit) contents of the currently visible (game) screen

* grabPalette (required):
   used to query the current palette (counterpart of setPalette)

Some rudimentary Doxygen comments were added, as well as an 
implementation in the SDL backend. I'll be happy to clear up any 
questions about them.

Cheers,
Max