Fix some header includes detected by clangd

There were some missing headers like <stddef.h> for `NULL`, <wayland-util.h>
for `wl_link` and <stdbool.h> for `true`/`false`.

Also this commit fixes that `labwc.h` and `ime.h` included each other.

include/config/touch.h

@@ -3,6 +3,7 @@
 #define LABWC_TOUCH_CONFIG_H
 
 #include <stdint.h>
+#include <wayland-util.h>
 
 struct touch_config_entry {
 	char *device_name;