[PATCH] add optional three-channel support to fl2k_file

Hello, attached is a patch to fl2k_file that introduces the -3 command line option. If this option is in use, fl2k_file will treat the input file as a sequence of frames of 3 samples for each of the red, green, and blue output channels. This implementation is not exactly optimal in CPU use, since the patch de-interleaves the input first, and the underlying library then proceeds to re-interleave it (in the weird hardware-specific order). This is because I didn't feel comfortable trying to redesign the fl2k_data_info_t structure to support interleaved data without guidance from the architect. But with a more flexible structure, these stages could be combined, improving the throughput. -- Riley Faelan