Allow exception handlers to be created which act over multiple catch ranges

[broneill]

If the catch ranges overlap, then combine them, reducing the size of the exception handler table.

[broneill]

This feature can be emulated by creating multiple handlers which then jump to a common location. The pattern is: store the exception variable to a common variable, and then goto. If this pattern is matched, then the handlers can be combined together automatically. If there's no variable store and just a goto, that should match too.