compositor: move libudev.h to evdev.h

Compositor core does not do anything with udev, so the header is not
needed there. Move the #include into evdev.h, from where it gets used by
compositor-drm.c, too.

Also fix the fallout:
tty.c: In function 'tty_create':
tty.c:143:2: warning: implicit declaration of function 'fstat'

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>

src/evdev.h

@@ -20,6 +20,8 @@
  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include <libudev.h>
+
 void
 evdev_add_devices(struct udev *udev, struct weston_input_device
 		  *input_base);