Remove the mallocs for the codecdata in the m4a parser and assume a maximum size...

Remove the mallocs for the codecdata in the m4a parser and assume a maximum size of 64 bytes (see comments in source).  Also clean up the alac_set_info() function a little and make it alignment-safe.  We still need to remove the seektable related mallocs.  Please report if any AAC or ALAC files stop playing in Rockbox after this commit - but it is not expected to cause problems.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@15861 a1c6a512-1295-4272-9138-f99709370657