Reorder functions to avoid forward declarations.

It isn't use anywhere else.

This avoids racing with the audio output thread (if it exists) on the
end date of the mixer input FIFO.

This avoids racing with decoder thread (audio input & mixer) w.r.t. the
FIFO timestamps.

Reported-By: Alessandro (ale5000)

Reported-By: Alessandro (ale5000)

- by default, fullscreen is performed on the same monitor as the one
  where the video is currently being played back.
- support for --qt-fullscreen-screennumber if the user wishes to force
  fullscreen on a given monitor.

This fixes trac #4712. Tested on Linux. Tests needed for Windows.

The audio input drops expired packets before they hit the mixer. Since
we only support a single input per mixer, the mixer check is mostly
redumdant.

Pointed-out-by: Fabian Greffrath <fabian@greffrath.com> (Debian BTS)

macosx: fixed disappearing repeat button images introduced in [8f79caa3e4b56c73c719bfa7c444cccbf203aa19]

Closes #4886

Main reason is that tt has the nicer subtitles support
Broken configurations (looking at you S3 and Matrox) will be able to use
the DirectDraw module.

Unsupported versions:
- Win9x (this is already the case)
- Win XP SP0, SP1
- Win 2000 (all editions)
- Windows 2003 SP0

Supported versions:
- Windows XP SP2, SP3
- Windows 2003 SP1
- Windows Vista, 7 and 2008