allow top keyword as column / table / alias name

implemented tests

Author: wumpz

src/main/jjtree/net/sf/jsqlparser/parser/JSqlParserCC.jjt

@@ -1078,7 +1078,7 @@ Normal names.
 String RelObjectName() :
 {    Token tk = null; String result = null; }
 {
-    (result = RelObjectNameWithoutValue() | tk=<K_VALUE> | tk=<K_VALUES> | tk=<K_INTERVAL>)
+    (result = RelObjectNameWithoutValue() | tk=<K_TOP> | tk=<K_VALUE> | tk=<K_VALUES> | tk=<K_INTERVAL>)
 
     { 
 		if (tk!=null) result=tk.image;
@@ -1109,7 +1109,7 @@ String RelObjectNameExt2():
   String result=null;
 } 
 {
-    ( result=RelObjectNameExt() | tk=<K_TOP> | tk=<K_FROM> )
+    ( result=RelObjectNameExt() | tk=<K_FROM> )
     {
         if (tk!=null) result=tk.image;
         return result;
@@ -1217,7 +1217,7 @@ PlainSelect PlainSelect() #PlainSelect:
             )
     ]
 
-    [top = Top() { plainSelect.setTop(top);    } ]
+    [ LOOKAHEAD(2) top = Top() { plainSelect.setTop(top);    } ]
 
     selectItems=SelectItemsList()
 

src/test/java/net/sf/jsqlparser/statement/select/SelectTest.java

@@ -3299,6 +3299,21 @@ public void testTrueFalseLiteral() throws JSQLParserException {
         assertSqlCanBeParsedAndDeparsed("SELECT * FROM tbl WHERE true OR clm1 = 3");
     }
 
+    @Test
+    public void testTopKeyWord() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT top.date AS mycol1 FROM mytable top WHERE top.myid = :myid AND top.myid2 = 123");
+    }
+
+    @Test
+    public void testTopKeyWord2() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT top.date");
+    }
+
+    @Test
+    public void testTopKeyWord3() throws JSQLParserException {
+        assertSqlCanBeParsedAndDeparsed("SELECT * FROM mytable top");
+    }
+
     @Test
     public void testRawStringExpressionIssue656() throws JSQLParserException {
         for (String c : new String[]{"u", "e", "n", "r", "b", "rb"}) {