py: Move to Python 3.4.0 compatibility.

Very little has changed.  In Python 3.4 they removed the opcode
STORE_LOCALS, but in Micro Python we only ever used this for CPython
compatibility, so it was a trivial thing to remove.  It also allowed to
clean up some dead code (eg the 0xdeadbeef in class construction), and
now class builders use 1 less stack word.

Python 3.4.0 introduced the LOAD_CLASSDEREF opcode, which I have not
yet understood.  Still, all tests (apart from bytecode test) still pass.
Bytecode tests needs some more attention, but they are not that
important anymore.