+ Redirect PyMem_{Del, DEL} to the object allocator's free() when
  pymalloc is enabled.  Needed so old extensions can continue to
  mix PyObject_New with PyMem_DEL.

+ This implies that pgen needs to be able to see the PyObject_XYZ
  declarations too.  pgenheaders.h now includes Python.h.  An
  implication is that I expect obmalloc.o needs to get linked into
  pgen on non-Windows boxes.

+ When PYMALLOC_DEBUG is defined, *all* Py memory API functions
  now funnel through the debug allocator wrapper around pymalloc.
  This is the default in a debug build.

+ That caused compile.c to fail:  it indirectly mixed PyMem_Malloc
  with raw platform free() in one place.  This is verbotten.