Editing and markup cleanup.

doc/src/sgml/ref/alter_table.sgml

doc/src/sgml/ref/create_index.sgml

doc/src/sgml/ref/create_language.sgml

doc/src/sgml/ref/create_table.sgml

doc/src/sgml/ref/create_trigger.sgml

doc/src/sgml/ref/create_type.sgml

doc/src/sgml/ref/create_user.sgml

doc/src/sgml/ref/create_view.sgml

doc/src/sgml/ref/declare.sgml

doc/src/sgml/ref/delete.sgml

doc/src/sgml/ref/drop_aggregate.sgml

doc/src/sgml/ref/drop_database.sgml

doc/src/sgml/ref/drop_function.sgml

doc/src/sgml/ref/drop_index.sgml

doc/src/sgml/ref/drop_language.sgml

doc/src/sgml/ref/drop_operator.sgml

doc/src/sgml/ref/drop_rule.sgml

doc/src/sgml/ref/drop_sequence.sgml

doc/src/sgml/ref/drop_table.sgml

doc/src/sgml/ref/drop_trigger.sgml