"CURRENT_ROLE" is not documented

While trying to understand whether there was any difference, I noticed
that CURRENT_ROLE is an undocumented synonymous for CURRENT_USER:

psql> SELECT CURRENT_ROLE;
current_user -- not a typo, it really says "current_user"
calvin

sh> grep -i CURRENT_ROLE doc/src/sgml/*/*.sgml doc/src/sgml/*.sgml
doc/src/sgml/keywords.sgml: <entry><token>CURRENT_ROLE</token></entry>

Is there a special reason why it does not appear in the documentation? If
not, I would suggest to apply the attached minimal documentation patch.

Also, there is a SESSION_USER, but no SESSION_ROLE. Not sure of the
rationale.

--
Fabien.