pidstatus(): Delete commented-out code testing for exit(255).

pidstatus(): Delete commented-out code testing for exit(255).

Pre-dating git, a test of wait(2)'s status having its top eight bits all
set was commented out an "I've no idea what this does" explanation.  The
top eight bits hold either exit(3)'s parameter or the signal that caused
the child to stop.  Either way, there are macros for pulling apart that
value and they're being used.  Perhaps they were broken on a much older
system.  Delete the comment, including its code.