w32_common: prevent display power management

Handling SC_MONITORPOWER doesn't seem to prevent the screen from
dimming. The recommended way to do this in Windows XP and Vista is to
call SetThreadExecutionState with ES_DISPLAY_REQUIRED. Windows 7 also
has the PowerCreateRequest/PowerSetRequest/PowerClearRequest APIs but
they're probably too complicated for this task.
Merge pull request #124 from rossy2401/w32-display-required

Prevent display power management in Windows
input: don't ignore press-only mouse button events

Before this commit, only mouse events with both down and up events
were processed. This caused a regression with ignoring mouse wheel
events in cocoa, because these don't distinguish between up and down.

Regression caused by 5b38a52.
demux_mkv: pass extradata for opus

Fixes playing 5.1 opus audio tracks.