Define _GNU_SOURCE if using gcc.

configure.in

-dnl $Id: configure.in,v 1.26 1995/01/08 11:14:07 ceder Exp $
+dnl $Id: configure.in,v 1.27 1995/10/23 06:57:14 ceder Exp $
 dnl Configuration for LysKOM
 dnl Copyright (C) 1993, 1994, 1995  Lysator Academic Computer Association.
 dnl
@@ -18,7 +18,7 @@ dnl Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 dnl
 dnl Please mail bug reports to bug-lyskom@lysator.liu.se. 
 dnl
-AC_REVISION($Revision: 1.26 $)
+AC_REVISION($Revision: 1.27 $)
 AC_INIT(src/server/lyskomd.h)
 AC_PREFIX_DEFAULT(/usr/lyskom)
 AC_PROG_CC
@@ -33,7 +33,8 @@ AC_ISC_POSIX
 AC_MINIX
 [if test -n "$GCC"; then
 	CFLAGS="$CFLAGS -Wall -ansi"
-	] KOM_COMPILER_CC_ACCEPTS([-pipe]) [
+	] AC_DEFINE(_GNU_SOURCE)
+	KOM_COMPILER_CC_ACCEPTS([-pipe]) [
 	DEPENDFLAG=-MM
 else
 	case "$CC" in