do_cmd_let():  Simple implementation to allow \let to be used to establish synonyms for macros.  This supports:
do_cmd_let():  Simple implementation to allow \let to be used to establish
synonyms for macros.  This supports:

	\let\newname = \oldname
	\let\newname\oldname

This is useful sometimes, and can at least avoid real errors at other times.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator