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/wozmon/wozmon.cc

@@ -125,7 +125,6 @@ int main() {
     gpio0->data = 1;
     uint32_t cur_addr = 0;
     uint32_t cur_data = 0;
-    bool writing = false;
 
     char inbuf[64] = {};
     char* inptr = inbuf;