Add ALTER FOREIGN DATA WRAPPER / RENAME and ALTER SERVER / RENAME

doc/src/sgml/ref/alter_foreign_data_wrapper.sgml

doc/src/sgml/ref/alter_server.sgml

src/backend/commands/alter.c

src/backend/commands/foreigncmds.c

src/backend/parser/gram.y

src/include/commands/defrem.h

src/test/regress/expected/foreign_data.out

src/test/regress/sql/foreign_data.sql