lib_socket_nsl

This macro figures out what libraries are required on this platform to link sockets programs.

The common cases are not to need any extra libraries, or to need -lsocket and -lnsl. We need to avoid linking with libnsl unless we need it, though, since on some OSes where it isn't necessary it will totally break networking. Unisys also includes gethostbyname() in libsocket but needs libnsl for socket().

AC_DEFUN([LIB_SOCKET_NSL],
[
	AC_SEARCH_LIBS([gethostbyname], [nsl])
	AC_SEARCH_LIBS([socket], [socket], [], [
		AC_CHECK_LIB([socket], [socket], [LIBS="-lsocket -lnsl $LIBS"],
		[], [-lnsl])])
])