Add qstr_info() function and bindings for unix port.
py: Msg in exception is no longer interned.
py: Fix bug with LOAD_METHOD; fix int->machine_int_t for small int.

LOAD_METHOD bug was: emitbc did not correctly calculate the amount of
stack usage for a LOAD_METHOD operation.

small int bug was: int was being used to pass small ints, when it should
have been machine_int_t.