Further optimised the filter vector math assembly for coldfire, and added assembly...

Further optimised the filter vector math assembly for coldfire, and added assembly filter vector math for ARM. Both make use of the fact that the first argument of the vector functions is longword aligned. * The ARM version is tailored for ARM7TDMI, and would slow down arm9 or higher. Introduced a new CPU_ macro for ARM7TDMI. Speedup for coldfire: -c3000 104%->109%, -c4000 43%->46%, -c5000 1.7%->2.0%. Speedup for PP502x: -c2000 66%->75%, -c3000 37%->48%, -c4000 11%->18%, -c5000 2.5%->3.7%

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@15304 a1c6a512-1295-4272-9138-f99709370657