Fix cannot build mencoder on amd64

Hi!
I cannot build mencoder on freebsd-7/amd64 successfully, like this:
{standard input}: Assembler messages:
{standard input}:1289: Error: can't encode register '%ch' in an
instruction requiring REX prefix.
{standard input}:1290: Error: can't encode register '%ah' in an
instruction requiring REX prefix.
{standard input}:1291: Error: can't encode register '%dh' in an
instruction requiring REX prefix.
make[3]: *** [osd.o] Error 1

After tried some guy's patch, it works on FreeBSD too.
I tried encoding some DVDs to x264 encoded no any problem found.