Avoiding infinite throw-catch loops

Previously I encountered a problem when doing bytecode instrumentation of try-catch blocks. The Java compiler sometimes emits exception table entries that register short regions as their own exception handlers. When code that can cause exceptions is inserted into the middle of these regions, an infinite loop results.

To avoid this with the ASM bytecode library, I just added a check in visitTryCatchBlock to see if the handler label was the same as the start label. If so, the function returns without passing the event along, removing the exception table entry. This can't break anything because if the handler was ever used under normal circumstances, it would trigger a thread-termination-resistant infinite loop, which I don't observe.