Add libinput based input device backend

While disable by default, passing --enable-libinput-backend to
./configure switches the input backend in weston's drm, fbdev and rpi
compositing backends to use libinput instead of udev-seat.c, evdev.c and
friends.

When enabled, weston now also depends on libinput >= 0.1.0.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
diff --git a/configure.ac b/configure.ac
index 00d7123..4db0ed1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -153,6 +153,16 @@
   PKG_CHECK_MODULES(DRM_COMPOSITOR, [libudev >= 136 libdrm >= 2.4.30 gbm mtdev >= 1.1.0])
 fi
 
+
+AC_ARG_ENABLE(libinput-backend, [  --enable-libinput-backend],,
+	      enable_libinput_backend=no)
+AM_CONDITIONAL([ENABLE_LIBINPUT_BACKEND], [test x$enable_libinput_backend = xyes])
+if test x$enable_libinput_backend = xyes; then
+  AC_DEFINE([BUILD_LIBINPUT_BACKEND], [1], [Build the libinput input device backend])
+  PKG_CHECK_MODULES(LIBINPUT_BACKEND, [libinput >= 0.1.0])
+fi
+
+
 PKG_CHECK_MODULES(COMPOSITOR, [$COMPOSITOR_MODULES])
 
 AC_ARG_ENABLE(wayland-compositor, [  --enable-wayland-compositor],,
@@ -506,6 +516,8 @@
 	FBDEV Compositor		${enable_fbdev_compositor}
 	RDP Compositor			${enable_rdp_compositor}
 
+	libinput Backend		${enable_libinput_backend}
+
 	Raspberry Pi BCM headers	${have_bcm_host}
 
 	Build Clients			${enable_clients}