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
videoplayer: adopt lateness detection and dropping to buffering
video player: present correct pts to user for a/v sync (after buffering in renderer)
vaapi: adopt to buffering in renderer