More detailed version head
Get audio from AvxSynth as well.

Based on a patch by 0x09 (tab@lavabit.com). The original patch
description as follows:

In this case since they both target 2.5, the only modifications
to input/audio/avs.c are linking av[ix]synth instead of loading,
and not being usable as an importer for regular audio files (only
scripts)*.

*The other one allows things like

--audiofile somefile.mp3 --ademuxer avs

and opens somefile with (e.g.) DirectShowSource. Since all we have
is ffms2 it's kind of pointless.
Fix compilation since AVCODEC_MAX_AUDIO_FRAME_SIZE was removed.

Using deprecated macro, but still better than broken.
Fix compilation with --disable-audio
configure: Add --disable-mp3 option
always use strict=-2 for aac

FFmpeg internal aac encoder needs this.
assume channels = 2 when can't get them
Skip useless lavr check when lavf is not available
Add an option to use r2204 style progress indicator
Add back "touhou" tune
Film Grain Optimization
Fade Compensation
Remove stats before renaming
Add a parameter to set level of writing options in User Data Unregistered SEI
Utilize internal threading in lavf/ffms
Auto VBV settings