window: Add a log handler for window.c clients

This way we can see what kind of error we get if we get an error.
diff --git a/clients/window.c b/clients/window.c
index 073ce53..2540cc9 100644
--- a/clients/window.c
+++ b/clients/window.c
@@ -4383,11 +4383,19 @@
 	}
 }
 
+static void
+log_handler(const char *format, va_list args)
+{
+	vfprintf(stderr, format, args);
+}
+
 struct display *
 display_create(int *argc, char *argv[])
 {
 	struct display *d;
 
+	wl_log_set_handler_client(log_handler);
+
 	d = malloc(sizeof *d);
 	if (d == NULL)
 		return NULL;