mbv: now with functioning timer interrupts!

And a few other nice things.
The bootloader now has an embedded wozmon!
If you know its offset, you can jump to it from the app.

mbv/Makefile

@@ -10,6 +10,10 @@ helloworld:  ## Build the helloworld app in docker
 wozmon:  ## Build the wozmon app in docker
 	docker build -o . --target export --build-arg TARGET=wozmon.bin .
 
+.PHONY: timer
+timer:  ## Build the timer app in docker
+	docker build -o . --target export --build-arg TARGET=timer.bin .
+
 .PHONY: dev-image
 dev-image:
 	docker build -t mbv-dev --target dev .