Specify maximum sample rate of MLP by defining the factor relative to 48000
instead of directly.
This makes clear that the code assumes the maximum sample rate to be
a multiple of 48000 and also removes the division from the MAX_BLOCKSIZE
macros, which causes an issue with the Solaris assembler where "/" is
a comment marker unless the --divide option is used.
Originally committed as revision 20026 to svn://svn.ffmpeg.org/ffmpeg/trunk