Remove not-really-standard implementation of CREATE TABLE's UNDER clause,

and revert documentation to describe the existing INHERITS clause
instead, per recent discussion in pghackers.  Also fix implementation
of SQL_inheritance SET variable: it is not cool to look at this var
during the initial parsing phase, only during parse_analyze().  See
recent bug report concerning misinterpretation of date constants just
after a SET TIMEZONE command.  gram.y really has to be an invariant
transformation of the query string to a raw parsetree; anything that
can vary with time must be done during parse analysis.

src/backend/parser/keywords.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/parser/keywords.c,v 1.86 2000/12/15 23:36:19 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/parser/keywords.c,v 1.87 2001/01/05 06:34:19 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -262,7 +262,6 @@ static ScanKeyword ScanKeywords[] = {
 	{"truncate", TRUNCATE},
 	{"trusted", TRUSTED},
 	{"type", TYPE_P},
-	{"under", UNDER},
 	{"union", UNION},
 	{"unique", UNIQUE},
 	{"unlisten", UNLISTEN},