Properly process try/finally blocks.

Properly process try/finally blocks.

In some circumstances, try/finally block can actually catch the exception:

function f() {
  try {
    throw 42;
  } finally {
    return 0;
  }
}

Therefore when propagating exception to v8::TryCatch, we must be sure
there is no try/finally blocks as well.

When bulding the messages we should be more conservative and expect that
any v8::TryCatch with no JS try/catch in between can potentionally
be the right exception handler.

Plus various minor refactorings.

BUG=1147
TEST=cctest/test-api/TryCatchAndFinallyHidingException, cctest/test-api/TryCatchAndFinally

Review URL: http://codereview.chromium.org/6526016

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6809 ce2b1a6d-e550-0410-aec6-3dcde31c8c00