support NetBSD's LOCAL_PEEREID, which works like SO_PEERCRED
simplify LDFLAGS, as -lrt and -lm should work everywhere; NetBSD 5 doesn't have libdl as it's built-in
our LDFLAGS simplifications failed; try again
OpenBSD's SO_PEERCRED takes a struct sockpeercred, not struct ucred
more LDFLAGS troubles