Fix documentation of information_schema.element_types
Fix documentation of information_schema.element_types

The documentation of the columns collection_type_identifier and
dtd_identifier was wrong.  This effectively reverts commits
8e1ccad51901e83916dae297cd9afa450957a36c and
57352df66d3a0885899d39c04c067e63c7c0ba30 and updates the name
array_type_identifier (the name in SQL:1999) to
collection_type_identifier.

closes bug #5926

adam8157/gpdb,jmcatamney/gpdb,techdragon/Postgres-XL,ashwinstar/gpdb,zeroae/postgres-xl,ovr/postgres-xl,zeroae/postgres-xl,postmind-net/postgres-xl,pavanvd/postgres-xl,xinzweb/gpdb,tpostgres-projects/tPostgres,ashwinstar/gpdb,arcivanov/postgres-xl,adam8157/gpdb,adam8157/gpdb,greenplum-db/gpdb,kmjungersen/PostgresXL,tpostgres-projects/tPostgres,lisakowen/gpdb,kmjungersen/PostgresXL,oberstet/postgres-xl,pavanvd/postgres-xl,arcivanov/postgres-xl,xinzweb/gpdb,lisakowen/gpdb,lisakowen/gpdb,oberstet/postgres-xl,pavanvd/postgres-xl,ovr/postgres-xl,adam8157/gpdb,pavanvd/postgres-xl,greenplum-db/gpdb,lisakowen/gpdb,xinzweb/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,yazun/postgres-xl,greenplum-db/gpdb,ashwinstar/gpdb,xinzweb/gpdb,adam8157/gpdb,zeroae/postgres-xl,snaga/postgres-xl,techdragon/Postgres-XL,postmind-net/postgres-xl,tpostgres-projects/tPostgres,oberstet/postgres-xl,postmind-net/postgres-xl,ashwinstar/gpdb,jmcatamney/gpdb,lisakowen/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,xinzweb/gpdb,pavanvd/postgres-xl,50wu/gpdb,kmjungersen/PostgresXL,50wu/gpdb,arcivanov/postgres-xl,50wu/gpdb,yazun/postgres-xl,tpostgres-projects/tPostgres,snaga/postgres-xl,snaga/postgres-xl,greenplum-db/gpdb,Postgres-XL/Postgres-XL,arcivanov/postgres-xl,jmcatamney/gpdb,tpostgres-projects/tPostgres,techdragon/Postgres-XL,ashwinstar/gpdb,snaga/postgres-xl,yazun/postgres-xl,arcivanov/postgres-xl,adam8157/gpdb,lisakowen/gpdb,xinzweb/gpdb,50wu/gpdb,adam8157/gpdb,yazun/postgres-xl,zeroae/postgres-xl,greenplum-db/gpdb,ovr/postgres-xl,50wu/gpdb,Postgres-XL/Postgres-XL,techdragon/Postgres-XL,oberstet/postgres-xl,postmind-net/postgres-xl,kmjungersen/PostgresXL,jmcatamney/gpdb,lisakowen/gpdb,ovr/postgres-xl,50wu/gpdb,Postgres-XL/Postgres-XL,xinzweb/gpdb,ashwinstar/gpdb,yazun/postgres-xl,50wu/gpdb,adam8157/gpdb,jmcatamney/gpdb,arcivanov/postgres-xl,kmjungersen/PostgresXL,ashwinstar/gpdb,postmind-net/postgres-xl,Postgres-XL/Postgres-XL,lisakowen/gpdb,xinzweb/gpdb,50wu/gpdb,zeroae/postgres-xl,greenplum-db/gpdb,techdragon/Postgres-XL,ovr/postgres-xl,jmcatamney/gpdb,Postgres-XL/Postgres-XL,oberstet/postgres-xl,snaga/postgres-xl,ashwinstar/gpdb