Frame Step forward with Sync Renderer does not update position

[cajhin]

(Minor issue that few users will care about, workaround exists - please disregard if there is no trivial fix)

To Recreate (latest 2.3.7 or old v1.9, doesn't matter):

1. Set Options>Playback>Output = Sync Renderer
2. restart (looks like stop+play does not completely reset the renderer?)
3. play video to 00:10 then pause
4. frame step forward five seconds
5. play

Result:

1. time display stayed at 00:10
2. audio plays from 00:10 to 00:15 while the video is still
3. after five seconds at 00:15, normal play resumes

Workaround:
After many framestep-forward, do one framestep-backward to sync time

Notes:

• framestep backwards updates the 'current position'
• other renderers update the position
• mpc-be behaves the same
• Sync renderer is cool, because it can usually framestep forward with 30fps (fluidly)

[clsid2]

There is no real framestep backwards. It is in reality just an ordinary seek.

Sync Renderer is practically unmaintained. So issues are low priority.
At quick glance I don't see any obvious differences in the code with regards to frame stepping when compared to EVR-CP.