Comment out unused code

Remove Spectrum synth flags and stereo-to-mono sample downmining code.

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
[test] Add format test for mod with ADPCM4 samples

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
[test] Update Oktalyzer loader test

Also test for 7-bit samples.

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Remove inaccurate comment from mod loader

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Update gitignore

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Rebase lzx decompressor on LGPL version from XAD

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Update changelog

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>