initial work on variable order statistics gathering.
5th order for now, and will trim out/compact uninteresting/sparse
sub-trees.
first cut at generating file containing trimmed variable-order
statistics.
more work on variable depth stats modelling. beginning on code
to extract stats vectors from compressed file.
work on extracting nodes from compressed message stats structure.
also refined compressed format.
more work on decoding compress statistics.
check for illegal use of range_encode_equiprobable.
output message_stats.c directly, instead of via stdout.
More work on variable order statistics.
fixed bugs with encoding and decoding compressed frequency
information.
separating out code for decompressing packed statistics file.
working on extracting frequency distribution vector for variable
order statistics for use in encoder/decoder.
release memory allocated during extraction of compressed
frequency data.
more work on variable order stats.
still major bugs.
various fixes to compressed statistics reading and writing.
looks like arithmetic coder bug is next remaining issue.
do more rigorous testing of arithmetic coder.
fix divide by zero error when decoding from 0-symbol alphabet.
fixing more bugs with compressed statistics handling.
improved debugging to track down remaining vector extraction
bugs.
fixed bugwith proessing CR/LF at end of lines.
fixed more bugs with compressed statistics handling.
now seems to work, subject to testing.
compresses and decompresses, but with worse performance than
the original fixed Order-3 version.  Need to debug that correct
stats are used to predict each character.