PPC: check for x-form asm constraint support
Originally committed as revision 18606 to svn://svn.ffmpeg.org/ffmpeg/trunk
PPC asm for AV_RL*()
PPC is normally big endian but has special little endian load/storeinstructions. Using these avoids a separate byteswap. This makes thevorbis decoder about 5% faster. Not much else uses little-endianread/write extensively.
GCC generates horrible PPC code for the default AV_[RW]B64 (which uses...