Support for `throw`ing inside catch block or nested try/catch structure

[Jamesits]

[Jamesits]

This can be solved by a global jmp_env stack.

[Jamesits]

Steps:

1. Setup a global stack in which stores jmp_envs and other useful information.
2. push() before current try macro, and pop() after try statement has finished.

step 2 can be done by using a while since on finish it went back to evaluate its value again.