pgsql: Add pg_has_role() family of privilege inquiry functions modeled

Log Message:
-----------
Add pg_has_role() family of privilege inquiry functions modeled after the
existing ones for object privileges. Update the information_schema for
roles --- pg_has_role() makes this a whole lot easier, removing the need
for most of the explicit joins with pg_user. The views should be a tad
faster now, too. Stephen Frost and Tom Lane.

Modified Files:
--------------
pgsql/doc/src/sgml:
func.sgml (r1.270 -> r1.271)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.270&r2=1.271)
pgsql/src/backend/catalog:
information_schema.sql (r1.29 -> r1.30)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/information_schema.sql.diff?r1=1.29&r2=1.30)
pgsql/src/backend/utils/adt:
acl.c (r1.120 -> r1.121)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/acl.c.diff?r1=1.120&r2=1.121)
pgsql/src/include/catalog:
catversion.h (r1.290 -> r1.291)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h.diff?r1=1.290&r2=1.291)
pg_proc.h (r1.377 -> r1.378)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h.diff?r1=1.377&r2=1.378)
pgsql/src/include/utils:
builtins.h (r1.260 -> r1.261)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/builtins.h.diff?r1=1.260&r2=1.261)