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/apps/timer/timer.cc

@@ -0,0 +1,47 @@
+#include <cstdint>
+
+#include "intc.h"
+#include "interrupts.h"
+#include "pol0.h"
+#include "timer.h"
+
+namespace {
+
+struct Gpio {
+    volatile uint32_t data;
+};
+
+Gpio* leds = reinterpret_cast<Gpio*>(GPIO0_BASE);
+Timer* timer;
+
+}
+
+void Timer0Isr() { 
+    static int counter = 0;
+    leds->data = counter++;
+
+    timer->Pet();
+    timer->ClearInterrupt();
+}
+
+void SetupTimer() {
+    timer = Timer::Instance(TIMER0_BASE);
+    timer->SetupAsWdt(100'000'000);
+    timer->EnableT1();
+
+    SetIsr(TIMER0_IRQN, Timer0Isr);
+    SetIrqEnabled(TIMER0_IRQN, true);
+    EnableInterrupts();
+}
+
+int main() {
+    leds->data = 0xa0;
+
+    SetupTimer();
+    SetExternalInterruptHandler(InterruptHandler);
+    EnableExternalInterrupts();
+
+    leds->data = 0xa1;
+
+    BiosWozmon();
+}