Give preference to iptables header files

Have the header files in the iptables source tree take precedence
over those from the kernel source. Otherwise, building the current
iptables from subversion just fails with kernels < 2.6.25.

Signed-off-by: Jan Engelhardt <jengelh@computergmbh.de>
diff --git a/configure.ac b/configure.ac
index 3314df4..e616329 100644
--- a/configure.ac
+++ b/configure.ac
@@ -40,15 +40,15 @@
 	-D_REENTRANT -Wall -Waggregate-return -Wmissing-declarations \
 	-Wmissing-prototypes -Wredundant-decls -Wshadow -Wstrict-prototypes \
 	-Winline -pipe -DIPTABLES_VERSION=\\\"$PACKAGE_VERSION\\\" \
-	-DIPT_LIB_DIR=\\\"\${iptdir}\\\" \
-	-I\"$kbuilddir/include\" -I\"$ksourcedir/include\""
+	-DIPT_LIB_DIR=\\\"\${iptdir}\\\"";
+kinclude_CFLAGS="-I\"$kbuilddir/include\" -I\"$ksourcedir/include\"";
 
 # Remove workarounds soon
 regular_CFLAGS="$regular_CFLAGS -Wno-aggregate-return \
 	-Wno-missing-declarations -Wno-missing-prototypes \
 	-Wno-redundant-decls -Wno-shadow -Wno-strict-prototypes -Wno-inline"
 
-AC_SUBST([regular_CFLAGS])
+AC_SUBST([regular_CFLAGS kinclude_CFLAGS])
 AC_SUBST([kbuilddir])
 AC_SUBST([ksourcedir])
 AC_SUBST([iptdir])