Vsync discussion

Those patches gives me flawless vsync with the 3.10 gpu libraries. Mileage could vary on the stable libs though, so probably has to be discussed

The first commit is actually an xbmc bug that I'll upstream ;)
The second one forces the use of vsync. I'm not sure anyone would actually want *not* having vsync enabled. It doesn't overwrite an existing FB_MULTI_BUFFER variable, for those needing 3.

It is *very* important (at least on my system) to keep the XBMC vsync setting on "Driver". Any other setting sooner or latter leads to a deadlock, probably due to the fact that xbmc is strangely doing the "eglSwapInterval" (i.e. enables vsync) for each and every frame ;)

On a side note, with this solved, the cubox-i has now become my daily device ;)