Tweak pseudocode log syntax.

It looks more natural to be less function-like.
Alias 'ALBUMARTIST' and 'ALBUM ARTIST' to 'PERFORMER'
Update vorbiscomment.py
Pre-verify TrueAudio frame checksums prior to decoding each frame.

This exposed some bugs in the substream_append routines
which only come up when the parent bitstream has callbacks set.
Implement substream_append() using read_bytes()

This reduces the number of slightly different bitstream methods needed
and allows for non-aligned substream reading.
Swap buffer handling macros for inline functions.

This makes it easier to swap in a different implementation down the line
in the event I want to handle the buffer using all pointers again.
Convert several short buffer handling functions to be inline.

This seems to provide a (very) modest speed boost
without turning all the routines into fragile macros.
Add documentation for new .clean() method interface.
Have BitstreamWriter's .write() methods work on big integers.

This replaces the ugly .write64() methods and now works on
any numeric Python object by breaking them down into manageable chunks
before turning values into low-level integers for processing by the
bitstream module.

This also applies to BitstreamRecorder and BitstreamAccumulator.
Add some sanity checking for BitstreamWriter methods.

Ensures non-numbers and negative numbers are rejected
in the proper places.
Update BitstreamReader to handle large reads properly.

Like with BitstreamWriter, this replaces the hackish read64() methods
and works properly on very large values by using low-level reads
in chunks and doing math on Python objects internally.
Update bitstream module's internal buffer sizes.

This is useful to minimize the number of calls to the C bitstream
functions by trying to cover as much of an unsigned value as possible.

Although it's straightforward on the BitstreamReader side
by using Py_BuildValue to parse an unsigned int,
it's trickier on the BitstreamWriter side since bits need to fit
into an unsigned int *and* long value (which may be the same size)
without overflow problems.
Simplify a few of the bitstream module functions.

There's a relatively large amount of Python math with a lot of
object creation/destruction, so it's best to keep them straightforward.
Several minor bugfixes.
Merge branch 'patch-1' of https://github.com/mtw00/python-audio-tools
Minor fix to ALBUM ARTIST alias.
Bump version to 2.21 beta 1