libfreerdp-gdi: added gdi_surface_frame_marker

Frame markes are not really implemented. Just SendFrameAcknowledge on
SURFACECMD_FRAMEACTION_END if settings->FrameAcknowledge > 0

This fixes issue #1352
Merge pull request #1353 from nfedera/fix-2013-07-15-01

libfreerdp-gdi: added gdi_surface_frame_marker