Silent build rules, using the same method as libutvideo.
Audio support

And some other old l-smash base functions
1. configure: Add --disable-* option for audio encoders
2. always use strict=-2 for aac
3. assume channels = 2 when can't get them
4. Skip useless lavr check when lavf is not available
5. Add --chpl-with-bom option
Supply a local copy of L-SMASH's importer.h in extras/lsmash/

This relieves the user of having to install this particular header
themselves with a different name, or from having to patch L-SMASH
to install it alongside lsmash.h.

The original move to liblsmash was intended to do away with having
to supply L-SMASH's source code internally, and this doesn't
change that.  It's simply easier to supply one compatibility
header than to force the user to know to copy it to the system
as lsmash_importer.h or to mess with L-SMASH's installation rules.
Add an option to use r2204 style progress indicator
Add back "touhou" tune
Utilize internal threading in lavf/ffms
Auto VBV settings
Log file
Encoding time
Level force
Profile force
Print video info with lavf/ffms demuxer
AviSynth 16bit hack
Skip bit depth filter when possible
Use f3kdb for bit depth conversion when needed

This fixes high bit depth AviSynth input with input-depth != 16 or BIT_DEPTH
Detect color matrix with lavf/ffms demuxer
Fix AviSynth color space converting matrix
Fix swscale color space converting matrix
Support "dgi" file extension
Support "vpy" file extension