configure.ac: Require libinput 0.8

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
diff --git a/configure.ac b/configure.ac
index e03c731..5720220 100644
--- a/configure.ac
+++ b/configure.ac
@@ -155,7 +155,7 @@
 fi
 
 
-PKG_CHECK_MODULES(LIBINPUT_BACKEND, [libinput >= 0.6.0])
+PKG_CHECK_MODULES(LIBINPUT_BACKEND, [libinput >= 0.8.0])
 PKG_CHECK_MODULES(COMPOSITOR, [$COMPOSITOR_MODULES])
 
 AC_ARG_ENABLE(wayland-compositor, [  --enable-wayland-compositor],,