Now we are able to CREATE PROCEDURAL LANGUAGE (Thanks, Jan).

src/backend/commands/Makefile

src/backend/commands/define.c

src/backend/commands/proclang.c

src/backend/commands/trigger.c

src/backend/parser/gram.y

src/backend/parser/keywords.c

src/backend/tcop/utility.c

src/backend/utils/Gen_fmgrtab.sh.in

src/backend/utils/cache/syscache.c

src/backend/utils/fmgr/fmgr.c

src/include/catalog/pg_language.h

src/include/commands/proclang.h

src/include/nodes/nodes.h

src/include/nodes/parsenodes.h

src/include/utils/rel.h

src/include/utils/syscache.h