Fix some out-of-date bits in the API docs
Rename TFrameInfo to FrameInfo
Decouple FrameInfo from FFMS_FrameInfo and rework invisible frame handling
Extract a bunch of stuff from indexing.cpp
Move declarations of concrete indexer types out of indexing.h
Move declarations of concrete video sources out of videosource.h
Move declarations of concrete audio sources out of audiosource.h
Move all of the common Haali stuff to its own utils file

This makes it so that utils.h doesn't have to shit up absolutely
everything with windows.h.
Regenerate build system
Add vapoursynth stuff to .gitignore
Extract some duplicated code in InitializeCodecContextFromHaaliInfo
Set has_b_frames to its final value before opening the codec

This ensures that the frames before the first bframe in the file are
delayed appropriately, as otherwise the frame immediately after the
first b-frame will be output before the b-frame.
Fix off-by-one error in MatroskaReader::Scan