Here's a new patch, which generates correct code for all variants of the class header syntax.

For now, I've implemented __build_class__ in Python; the built-in function by that name imports the build_class module and calls its build_class function.  (I'll later redo this in C.)

This is still rough; I didn't even delete the old BUILD_CLASS opcode.  But only a few unit tests fail (especially the ast and compiler tests).  There are no unit tests for the new functionality.  There is no documentation.

Failing tests:
    test_ast test_compiler test_ctypes test_descr test_grp test_pep292


File Added: meta.patch