fix seek() with no previous frame displayed allow stepping forwards through a video source frame by frame
fix seek() with no previous frame displayed
allow stepping forwards through a video source frame by frame

mpasternak/michaldtz-fixes-518-522,odyaka341/pyglet,google-code-export/pyglet,cledio66/pyglet,Austin503/pyglet,mpasternak/pyglet-fix-issue-518-522,qbektrix/pyglet,cledio66/pyglet,shaileshgoogler/pyglet,odyaka341/pyglet,arifgursel/pyglet,mpasternak/pyglet-fix-issue-552,qbektrix/pyglet,xshotD/pyglet,qbektrix/pyglet,kmonsoor/pyglet,mpasternak/michaldtz-fix-552,google-code-export/pyglet,shaileshgoogler/pyglet,Alwnikrotikz/pyglet,arifgursel/pyglet,qbektrix/pyglet,mpasternak/pyglet-fix-issue-552,google-code-export/pyglet,Austin503/pyglet,odyaka341/pyglet,Alwnikrotikz/pyglet,qbektrix/pyglet,mpasternak/pyglet-fix-issue-518-522,kmonsoor/pyglet,odyaka341/pyglet,mpasternak/michaldtz-fixes-518-522,shaileshgoogler/pyglet,gdkar/pyglet,xshotD/pyglet,mpasternak/pyglet-fix-issue-518-522,mpasternak/pyglet-fix-issue-552,odyaka341/pyglet,google-code-export/pyglet,gdkar/pyglet,kmonsoor/pyglet,Austin503/pyglet,Alwnikrotikz/pyglet,Austin503/pyglet,kmonsoor/pyglet,arifgursel/pyglet,Austin503/pyglet,mpasternak/pyglet-fix-issue-552,mpasternak/michaldtz-fixes-518-522,mpasternak/michaldtz-fixes-518-522,gdkar/pyglet,arifgursel/pyglet,gdkar/pyglet,mpasternak/pyglet-fix-issue-518-522,xshotD/pyglet,xshotD/pyglet,mpasternak/michaldtz-fix-552,gdkar/pyglet,xshotD/pyglet,mpasternak/michaldtz-fix-552,google-code-export/pyglet,cledio66/pyglet,shaileshgoogler/pyglet,mpasternak/michaldtz-fix-552,kmonsoor/pyglet,Alwnikrotikz/pyglet,shaileshgoogler/pyglet,cledio66/pyglet,arifgursel/pyglet,cledio66/pyglet,Alwnikrotikz/pyglet