compositor-x11: Return number of events processed

The event handler is supposed to return 0 if no events were handled and
a positive number if events were handled.  event always end up being NULL
however, so we always return 0.
diff --git a/src/compositor-x11.c b/src/compositor-x11.c
index d23553e..edb6f04 100644
--- a/src/compositor-x11.c
+++ b/src/compositor-x11.c
@@ -619,8 +619,10 @@
 	uint32_t *k;
 	uint32_t i, set;
 	wl_fixed_t x, y;
+	int count;
 
 	prev = NULL;
+	count = 0;
 	while (x11_compositor_next_event(c, &event, mask)) {
 		switch (prev ? prev->response_type & ~0x80 : 0x80) {
 		case XCB_KEY_RELEASE:
@@ -756,6 +758,7 @@
 			break;
 		}
 
+		count++;
 		if (prev != event)
 			free (event);
 	}
@@ -774,7 +777,7 @@
 		break;
 	}
 
-	return event != NULL;
+	return count;
 }
 
 #define F(field) offsetof(struct x11_compositor, field)