Include config.h in src/libudev/Makefile.am to provide needed #define's

This commit provides needed #define's that provide structures that
are found at configure time.  It also reverts commit

    91ce21b2d7

to avoid redefinitions of _GNU_SOURCE.

Signed-off-by: Anthony G. Basile <blueness@gentoo.org>

src/libudev/Makefile.am

@@ -5,6 +5,7 @@ LIBUDEV_REVISION=0
 LIBUDEV_AGE=2
 
 AM_CPPFLAGS = \
+	-include $(top_builddir)/config.h \
 	-DUDEV_CONF_FILE=\"$(udevconffile)\" \
 	-DUDEV_HWDB_BIN=\"$(udevhwdbbin)\" \
 	-I $(top_srcdir)/src/udev

src/libudev/libudev-monitor.c

@@ -17,8 +17,6 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#define _GNU_SOURCE
-
 #include <stdio.h>
 #include <stdlib.h>
 #include <stddef.h>

src/libudev/log.c

@@ -18,7 +18,6 @@
   You should have received a copy of the GNU Lesser General Public License
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
-#define _GNU_SOURCE
 
 #include <stdarg.h>
 #include <stdio.h>

src/libudev/path-util.c

@@ -19,8 +19,6 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#define _GNU_SOURCE
-
 #include <assert.h>
 #include <string.h>
 #include <unistd.h>

src/libudev/util.c

@@ -19,8 +19,6 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#define _GNU_SOURCE
-
 #include <assert.h>
 #include <string.h>
 #include <unistd.h>