Followup to previous commit; change fd_mask from signed to unsigned as it should have been to start with.  The implications of that are not pleasant when combined with >> as it breaks on multiples of NFDBITS. Right shifting of a signed value fills with a copy of the sign bit, not a zero.
Followup to previous commit; change fd_mask from signed to unsigned as
it should have been to start with.  The implications of that are not
pleasant when combined with >> as it breaks on multiples of NFDBITS.
Right shifting of a signed value fills with a copy of the sign bit,
not a zero.

Reported by:	bde

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase