Default values for function arguments

doc/src/sgml/func.sgml

doc/src/sgml/ref/create_function.sgml

doc/src/sgml/xfunc.sgml

src/backend/catalog/namespace.c

src/backend/catalog/pg_aggregate.c

src/backend/catalog/pg_proc.c

src/backend/commands/functioncmds.c

src/backend/commands/proclang.c

src/backend/nodes/copyfuncs.c

src/backend/nodes/equalfuncs.c

src/backend/parser/gram.y

src/backend/parser/parse_func.c

src/backend/tcop/utility.c

src/backend/utils/adt/ruleutils.c

src/bin/pg_dump/pg_dump.c

src/include/catalog/catversion.h

src/include/catalog/namespace.h

src/include/catalog/pg_attribute.h

src/include/catalog/pg_class.h

src/include/catalog/pg_proc.h