Rewrite InterruptHandler to use RAII

[Petronous]

Also allows recursive usage without the different levels knowing about each other, by moving the "old" fields into the instantiated object, where they always restore to the previous state in a stack-like manner. Tested quite thoroughly in the Transpose Example.

The previous version was poorly made:

• difficult to make sure that the handler actually cleans up under all circumstances
• no new Register calls could be made in between the first Register and Unregister without breaking the class, this would force any lower scope to worry about what the upper scopes did

And so I felt a rewrite was necessary