Merge pull request #3 from OpenELEC/dualaudio-fix

fix build on non-RPi platforms, buildissue introduced with adding dual audio support
VideoRenerers: add buffering
add buffering for GLES
WinRenderer: add buffering
DXVA: activate buffering in renderer
linuxrenderer: delete all textures on reconfigure
drop frame counter in application, ask render manager instead
vaapi: adopt to buffering in renderer
add buffering - some documentation
RenderManager: only flip free buffer if player has added something
move NUM_BUFFERS up to BaseRenderer.h
OverlayRenderer: align buffers with index in renderManager
add buffering - submit absolute time to render buffers
RenderManager: some rework, squash add buffering
dvdplayer: disable buffering unil dropping is improved
RenderManager: skip very late frames in render buffer
renderbuffers: drop enable/disable in this iteration
RenderManager: add method SetSpeed
OMXPlayer: adapt to buffering
overlays: squash to b0b5c7c825b0265c5e7c888a48a76d11eb719246