Adds ui64 (uint64_t) as a possible type for SpecifierOpt. This enables
 use of uint64_t options with SpecifierOpt such as channel_layout
 when expressed as a 64 bit channel mask.
Signed-off-by: pkviet <pkv.stream@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>