internal filters: enable avisynth support
Merge pull request #132 from m0vie/avisynth

Use LAV Splitter by default to demux AviSynth script.

This avoids using the old VFW interface that is said to be less stable than directly using AviSynth through ffmpeg. Note that this means AviSynth is still required to demux the scripts.
PGS Subtitles: Fix a crash in some cases.

Mimic the change for DVB subtitles just for consistency.
Cosmetics for MoveVideoWindow() method.
DVB: Don't update stats when channel is not active.
DVB: Show current event time in the status bar
DVB: Make use out of the DVBState struct.
Mpeg2SectionData: Minor refactioring of the ParseEIT() method
DVB: Cosmetic for SetChannel()
Cosmetics for timers.
Cosmetics for stats.
DVB: Fix time calculations

StartTime was day off in certain cases.
DVB: Add channel name to snapshot filename
DVB: Add only supported services.
DVB: Add context menu to navigation dialog.

Use std::vector to store channel in order to get better sort abilities.