move shared parts from VertexManager::vFlush into VideoCommon
fix ogl video config crash

This will happen when playing on any other backend than ogl which have a non-trival GLInterface::GetMode() method.
rename UpdateViewport to SetViewport like all others setters in RenderBase.h
move perfquery enable checks into videocommon (caller side)
use EFBRectangle for scissor rect

This one is backend independed. The backend should recalc such things on their own.
merge some common parts of Swap() into VideoCommon