Revert "Use cellvars instead of varnames."

This reverts commit 70b7924ccb5251f3a6c5de2be40995db0cdc6b4f.

Conflicts:
	bundle/cpython-33.dgbundle
	bundle/cpython-34.dgbundle
	core/14.generator.dg
	core/15.generator.names.dg
Rename some attributes, refactor some stuff.
Properly store top-level docstrings.