significant improvements include:
- char flags in ongakukan_adp_lib.c have all, with one exception, been made to bools.
-- ATM, sample_mode will remain a char.
-- several other variables have been removed. they did not affect decoding in any significant way.
-- init_ongakukan_adpcm now accepts at least one bool as an argument for a total of four arguments.
-- many function from lib renamed to follow external lib function naming standard.
- simplified ongakukan_adp_decoder.c
-- decode_ongakukan_adp in particular benefited from this code simpification; loop is now re-done so all samples are copied to outbuf when they're made available.
-- as a consequence of this, at least one var was removed entirely, while others have been redefined into different purposes; samples_filled is now a bool var that flags whether or not all available samples were decoded.
-- init_ongakukan_adp has four arguments as well, and accepts at least one bool as an argument of its own.
-- streamfile is now close there as well instead of in the external decoder lib.
- adp_ongakukan.c saw much simpified code as well; meta checks have been relaxed significantly, which meant the removal of several var and at least three vars repurposed into bools.
-- supposed_size is introduced as an entirely new var; it now calculates the supposed file size of an ADP file with several 32-bit fields from the first byte as a base.
-- consequently, file_size checks are now made against supposed_size.
- as a consequence of all of the above, riff.c has now lost an additional RIFF size check; initially if RIFF chunk reported a big-enough size than RIFF file realistically has, it would be enough for vgmstream to stop working with said file.
