fix compress filter for big endian machines

fix compress filter for big endian machines

This was broken since day one as it depended on little-endianness. Fix
it by checking the byte sex in configure and let the decoders
produce host endian 16 bit audio output by using the new
write_int16_host_endian() inline function in filter.h

This allows to omit the ugly byte-swapping in osx_write we've had
before.