pgsql: Remove traces of otherwise unused RELKIND_SPECIAL symbol.

Log Message:
-----------
Remove traces of otherwise unused RELKIND_SPECIAL symbol. Leave the psql bits
in place though, so that it plays nicely with older servers.

Per discussion.

Modified Files:
--------------
pgsql/doc/src/sgml:
catalogs.sgml (r2.122 -> r2.123)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml.diff?r1=2.122&r2=2.123)
pgsql/src/backend/access/heap:
heapam.c (r1.212 -> r1.213)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/access/heap/heapam.c.diff?r1=1.212&r2=1.213)
pgsql/src/backend/catalog:
dependency.c (r1.53 -> r1.54)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/dependency.c.diff?r1=1.53&r2=1.54)
pgsql/src/bin/psql:
describe.c (r1.135 -> r1.136)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/describe.c.diff?r1=1.135&r2=1.136)
tab-complete.c (r1.151 -> r1.152)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/tab-complete.c.diff?r1=1.151&r2=1.152)
pgsql/src/include/catalog:
pg_class.h (r1.91 -> r1.92)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_class.h.diff?r1=1.91&r2=1.92)