Optimize files for size & fix credits sound bug

It seems that even on a class 10 sdhc card, there is still an I/O bottleneck here.
Although additional compression will require slightly more CPU, there should still
be enough cycles to spare without affecting the framerate by any noticable amount.

The credit sound bug was fixed by changing its audio file to a rate of 32000hz.
Replaced some sounds with unclear copyright with new ones from 0.3.x and changed frequencies all to 32000hz

Changed the files to 32000hz to fix the sound pitch bug and to avoid having to resample
to 32000hz.  The space gained from compressing the images in the last commit should
make up for the extra space requirements for this and there shouldn't be any noticeable
difference in frame output rate.