need a special cpp macro like _XPG4 defined or the name buffer would
need to be dynamically allocated based on pathconf(), which is
undesirably complicated. Instead 255 is used as a suitably sized NAME_MAX
and 1024 in place of PATH_MAX.
include stdlib.h to define NULL; BSD/OS managed to define it in
one of the other files already included, but that was not portable.
Thanks for pointing these issues out for Linux, Brian.