configure: Pick up libseccomp include path

openSUSE 12.3 has seccomp.h in /usr/include/libseccomp-1.0.1,
so add `pkg-config --cflags libseccomp` output to QEMU_CFLAGS.

Cc: qemu-stable@nongnu.org
Signed-off-by: NAndreas Färber <afaerber@suse.de>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

configure

@@ -1499,6 +1499,7 @@ libs_softmmu="$libs_softmmu -lz"
 if test "$seccomp" != "no" ; then
     if $pkg_config --atleast-version=1.0.0 libseccomp --modversion >/dev/null 2>&1; then
         libs_softmmu="$libs_softmmu `$pkg_config --libs libseccomp`"
+        QEMU_CFLAGS="$QEMU_CFLAGS `$pkg_config --cflags libseccomp`"
 	seccomp="yes"
     else
 	if test "$seccomp" = "yes"; then