[modules/layout] add a new - generic - layout module

Add a new module "layout" that will eventually evolve into the only
keyboard layout module.

Right now, it uses an external binary (get-kbd-layout) to determine the
layout of a keyboard device (because I did not manage to call libX11
with ctypes correctly).

see #788
see #790

util/Makefile

@@ -0,0 +1,13 @@
+CC=gcc
+CFLAGS=
+
+%.o: %.c
+	$(CC) -c -o $@ $< $(CFLAGS)
+
+../bin/get-kbd-layout: layout.o
+	$(CC) -o $@ layout.o -lX11
+
+.PHONY: clean
+
+clean:
+	rm -f *.o