Bring PostgreSQL functions closer to the current level of PL/pgSQL:
- upgrade PL/pgSQL functions to the $$ notation (recommended since pg8.0, jan 2005).
- get rid of backslash usages in function definitions
- drop aliases in favor of named function arguments (recommended since pg8.0)
- fix wrong function_args, add missing function_args, align default semantics
with the defaults in pg (providing "null" as default means the argument is
optional).
- change return types of triggers from "opaque" to "trigger" (recommended since pg8.0)
- unify names of triggers *_tr
- removed some version dependencies of pg 7.2 and 7.3
