Fix port signedness calculation.
Fix port signedness calculation.

This fixes the sign calculation for port padding. It also reports if
the padding will be signed or not in the warning message. The inout
calculation may not be correct. It requires both the signal and the
port to be signed, but inout is not currently padded anyway.

CastMi/iverilog,CastMi/iverilog,CastMi/iverilog,themperek/iverilog,themperek/iverilog,themperek/iverilog