library/int8.m:
library/uint8.m:
Add num_zeros/1, num_ones/1, num_leading_zeros/1, num_trailing_zeros/1 and
reverse_bits/1.
library/int16.m:
Implement num_trailing_zeros/1 by calling the unsigned version.
tests/hard_coded/Mmakefile:
tests/hard_coded/bit_twiddle_int8.{m,exp}:
tests/hard_coded/bit_twiddle_uint8.{m,exp}:
Add tests of the new operations.
