Extend syntax of CREATE FUNCTION to resemble SQL99.

doc/src/sgml/ref/create_function.sgml

doc/src/sgml/release.sgml

src/backend/commands/functioncmds.c

src/backend/nodes/copyfuncs.c

src/backend/nodes/equalfuncs.c

src/backend/parser/gram.y

src/backend/parser/keywords.c

src/backend/tcop/postgres.c

src/backend/tcop/utility.c

src/bin/pg_dump/pg_dump.c

src/include/commands/defrem.h

src/include/nodes/nodes.h

src/include/nodes/parsenodes.h