Adding RM support to Rockbox

by MT for Rockbox

Rockbox already supports a wide range of codecs, it still, however, does not have support for RM. The main aim of the project, thus, is to add support for RM format, and to have enough fixed-point decoders to handle the commonly available RM files. Primary goal : Have at least one target play cook encoded audio in RM container. secondary goal : addition of another codec(s).