Extend GENH to support little-endian "Gamecube" DSP ADPCM coefficients, for some 3DS titles.

This involves a reinterpretation of byte 0x30 (coef type). Formerly this byte took on only two values, to indicate how the ADPCM coefficients (aka codebook) were stored:
0 - normal coefs: all 16 coefs interleaved into one array, offset given at 0x24 for left, 0x28 for right
1 - split coefs: 8 coefs in the main array, additional offset to 2nd array given at 0x34 for left, 0x38 for right

Now I am considering this to be indicated only by bit 0 of the coef type. Bit 1 is taking on an additional interpretation, if it is set, we consider the coefficients to be little endian rather than the normal big endian.

This should maintain backwards compatibility with old GENH files, which should have only used the value 0 or 1.

Thus, in effect we have:
0: normal, big endian
1: split, big endian
2: normal, little endian
3: split, little endian

I don't know of any situation in which 3 would be used (yet), but I'm sure devs will continue to surprise me.
clean up some warning-causing ugliness