Fixed Altivec.

[Ryan C. Gordon]

svn revision #409 fixes the Altivec mesh rendering codepath.

It definitely works in both debug and release mode on LinuxPPC. It had
to do with counting on some variables (local and global) being aligned
to 16 bytes.

zakk, if you could try it on Mac OS and see if it works there, I'd
appreciate it. Just toggle com_altivec and see if the Quake 3 logo on
the main menu vanishes...you don't need to restart to toggle com_altivec.

Tim, I just wedged a "#define ALIGN16" into renderer/tr_local.h. There's
almost certainly a better place for this (qcommon.h?), but I'll leave
that to your discretion.

--ryan.