libFLAC/md5.c : Massive refactoring of format_input_ function.
libFLAC/md5.c : Massive refactoring of format_input_ function.

This refactoring is in preparation for fixing the cast-align warning when
compiling on ARM (and possibly others). Testing on stereo 16 bit files
suggests that the difference between the performance of this code and the
old code is negligible (tested only on amd64/linux).

waitman/flac,waitman/flac,waitman/flac,waitman/flac,waitman/flac