add OSF/1 LDSHARED; add IRIX5 conditional for sockets

configure.in

@@ -115,6 +115,7 @@ then
 	SunOS/4*) LDSHARED="ld";;
 	SunOS/5*) LDSHARED="ld -G";;
 	hp*|HP*) LDSHARED="ld -b";;
+	OSF*) LDSHARED="ld -shared -expect_unresolved \"*\"";;
 	DYNIX/ptx*) LDSHARED="ld -G";;
 	*)	LDSHARED="ld";;
 	esac
@@ -145,9 +146,18 @@ AC_MSG_RESULT($LINKFORSHARED)
 AC_CHECK_LIB(dl, dlopen)	# Dynamic linking for SunOS/Solaris and SYSV
 AC_CHECK_LIB(dld, shl_load)	# Dynamic linking for HP-UX
 AC_CHECK_LIB(sun, getpwnam)	# NIS (== YP) interface for IRIX 4
+# The following three (nsl,inet,socket) are needed on Sequent;
+# the order of checking must be this.  Most SVR4 platforms will
+# need -lsocket and -lnsl.  However on SGI IRIX 5, these exist but
+# broken.  I see no elegant solution (probably CHECK_LIB should be
+# fixed to only add the library if the given entry point is not
+# satisfied without it).
+if test "`uname -s`" != IRIX
+then
 AC_CHECK_LIB(nsl, t_open, [LIBS="-lnsl $LIBS"]) # SVR4
 AC_CHECK_LIB(inet, gethostbyname, [LIBS="-linet $LIBS"], [], -lnsl) # Sequent
 AC_CHECK_LIB(socket, socket, [LIBS="-lsocket $LIBS"], [], $LIBS) # SVR4 sockets
+fi
 
 AC_MSG_CHECKING(for --with-readline)
 AC_ARG_WITH(readline, [--with-readline=DIRECTORY GNU readline], [