Add DEC and SESSION_USER as reserved words.

Move around a few other keywords which were not in the right category.
DEC and SESSION_USER are not yet committed to gram.y,
 since I'm in the middle of working on JOIN syntax too.

doc/src/sgml/syntax.sgml

@@ -94,15 +94,18 @@ VACUUM VERBOSE
      are allowed to be present as column labels, but not as identifiers:
 
      <programlisting>
-CASE COALESCE CROSS CURRENT 
+CASE COALESCE CROSS CURRENT CURRENT_USER 
+DEC DECIMAL 
 ELSE END
 FALSE FOREIGN 
 GLOBAL GROUP 
 LOCAL
-NULLIF
+NULLIF NUMERIC 
 ORDER 
 POSITION PRECISION 
+SESSION_USER 
 TABLE THEN TRANSACTION TRUE
+USER 
 WHEN
      </programlisting>
 
@@ -115,9 +118,9 @@ ADD ALL ALTER AND ANY AS ASC
 BEGIN BETWEEN BOTH BY
 CASCADE CAST CHAR CHARACTER CHECK CLOSE
  COLLATE COLUMN COMMIT CONSTRAINT CREATE
- CURRENT_DATE CURRENT_TIME CURRENT_TIMESTAMP CURRENT_USER
+ CURRENT_DATE CURRENT_TIME CURRENT_TIMESTAMP 
  CURSOR
-DECIMAL DECLARE DEFAULT DELETE DESC DISTINCT DROP
+DECLARE DEFAULT DELETE DESC DISTINCT DROP
 EXECUTE EXISTS EXTRACT
 FETCH FLOAT FOR FROM FULL
 GRANT 
@@ -125,13 +128,13 @@ HAVING
 IN INNER INSERT INTERVAL INTO IS
 JOIN 
 LEADING LEFT LIKE LOCAL
-NAMES NATIONAL NATURAL NCHAR NO NOT NULL NUMERIC
+NAMES NATIONAL NATURAL NCHAR NO NOT NULL 
 ON OR OUTER
 PARTIAL PRIMARY PRIVILEGES PROCEDURE PUBLIC
 REFERENCES REVOKE RIGHT ROLLBACK
 SELECT SET SUBSTRING
 TO TRAILING TRIM 
-UNION UNIQUE UPDATE USER USING
+UNION UNIQUE UPDATE USING
 VALUES VARCHAR VARYING VIEW
 WHERE WITH WORK 
      </programlisting>
@@ -183,7 +186,7 @@ CASCADED CATALOG COLLATION CONNECT CONNECTION
  CONTINUE CONVERT CORRESPONDING COUNT
 DATE DEALLOCATE DEC DESCRIBE DESCRIPTOR
  DIAGNOSTICS DISCONNECT DOMAIN 
-END-EXEC ESCAPE EXCEPT EXCEPTION EXEC EXTERNAL 
+ESCAPE EXCEPT EXCEPTION EXEC EXTERNAL 
 FIRST FOUND
 GET GO GOTO 
 IDENTITY INDICATOR INPUT INTERSECT
@@ -192,7 +195,7 @@ MAX MIN MODULE
 OCTET_LENGTH OPEN OUTPUT OVERLAPS 
 PREPARE PRESERVE 
 ROWS
-SCHEMA SECTION SESSION SESSION_USER SIZE SOME 
+SCHEMA SECTION SESSION SIZE SOME 
  SQL SQLCODE SQLERROR SQLSTATE SUM SYSTEM_USER
 TEMPORARY TRANSLATE TRANSLATION 
 UNKNOWN UPPER USAGE