pgsql: Speed up information schema privilege views Instead of expensive

Log Message:
-----------
Speed up information schema privilege views

Instead of expensive cross joins to resolve the ACL, add table-returning
function aclexplode() that expands the ACL into a useful form, and join
against that.

Also, implement the role_*_grants views as a thin layer over the respective
*_privileges views instead of essentially repeating the same code twice.

fixes bug #4596

by Joachim Wieland, with cleanup by me

Modified Files:
--------------
    pgsql/src/backend/catalog:
        information_schema.sql (r1.58 -> r1.59)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/information_schema.sql?r1=1.58&r2=1.59)
    pgsql/src/backend/utils/adt:
        acl.c (r1.150 -> r1.151)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/acl.c?r1=1.150&r2=1.151)
    pgsql/src/include/catalog:
        catversion.h (r1.554 -> r1.555)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/catversion.h?r1=1.554&r2=1.555)
        pg_proc.h (r1.554 -> r1.555)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_proc.h?r1=1.554&r2=1.555)
    pgsql/src/include/utils:
        acl.h (r1.109 -> r1.110)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/utils/acl.h?r1=1.109&r2=1.110)