Add a failing test of exceptions caught within finally blocks.
Record the last initial value of context.next as context.prev.
Record the beginning location of try statements in leap.TryEntry.
Call updateContextPrevLoc at the beginning of try/catch/finally blocks.
Assert redundant marking does not change values of location literals.
Reflect static knowledge about try statements into the runtime.

This will eventually remove the need for context.pushTry, .popCatch, and
.popFinally, as discussed in #84.
Store reflected try statement information in the Context object.
No more context.pushTry, .popCatch, or .popFinally, yay!

Fixes #84.