named OPTIMIZED, which matches compile.c and makes more sense for
classes

revamp call signature for PythonVMCode.__init__; doesn't really matter
'cuz this code is going to be refactored out of existence

add generateClassCode and modify Func & Lambda generation

add support for nodes Classdef, Keyword,

fix CallFunc to generate right op arg when calling w/ keywords

add ugly hack to properly compute offsets when the same stack ref is
used multiple times