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/app.ld

@@ -1,6 +1,6 @@
 MEMORY
 {
-    RAM (rwx) : ORIGIN = 0x00000800, LENGTH = 14336
+    RAM (rwx) : ORIGIN = 0x80000000, LENGTH = 0x10000000
 }
 
 _vector_table = 0x0;
@@ -37,6 +37,6 @@ SECTIONS
 
     _heap_begin = .;
 
-    _initial_stack_pointer = 16384;
-    _heap_end = _initial_stack_pointer - 1024;
+    _initial_stack_pointer = 0x90000000;
+    _heap_end = 0x8f000000; /* leave 1M for the stack */
 }