Removed WITH_CLEANUP_START, WITH_CLEANUP_FINISH, BEGIN_FINALLY, END_FINALLY, CALL_FINALLY and POP_FINALLY bytecodes.
Replaced with RERAISE and WITH_EXCEPT_FINISH bytecodes.
The compiler now generates different code for exceptional and non-exceptional branches for 'with' and 'try-except'
statements. For 'try-finally' statements the 'finally' block is replicated for each exit from the 'try' body.

