HHH-6672 - Remove UNION support from 5.x grammars

(cherry picked from commit dd4f809)

Author: sebersole

hibernate-core/src/main/antlr/hql.g

@@ -74,7 +74,6 @@ tokens
 	SOME="some";
 	SUM="sum";
 	TRUE="true";
-	UNION="union";
 	UPDATE="update";
 	VERSIONED="versioned";
 	WHERE="where";
@@ -298,10 +297,6 @@ insertablePropertySpec
 	}
 	;
 
-union
-	: queryRule (UNION queryRule)*
-	;
-
 //## query:
 //##     [selectClause] fromClause [whereClause] [groupByClause] [havingClause] [orderByClause];
 
@@ -805,7 +800,7 @@ compoundExpr
 	;
 
 subQuery
-	: union
+	: queryRule
 	{ #subQuery = #([QUERY,"query"], #subQuery); }
 	;
 

hibernate-core/src/test/java/org/hibernate/test/hql/HqlParserTest.java

@@ -33,13 +33,7 @@
  * works properly (i.e. no unexpected syntax errors).
  * todo this should be a unit test.
  */
-public class HqlParserTest{
-
-
-	@Test
-    public void testUnion() throws Exception {
-		parse("from Animal a where a in (from Cat union from Dog) ");
-	}
+public class HqlParserTest {
 
 	/**
 	 * Section 9.2 - from *