fix parser bug

src/test/java/com/alibaba/druid/sql/OracleTest.java

@@ -27,4 +27,6 @@ public class OracleTest extends TestCase {
         }
         System.out.println(text);
 	}
+	
+	
 }

src/test/java/com/alibaba/druid/sql/parser/SQLLexerTest2.java

@@ -24,4 +24,29 @@ public class SQLLexerTest2 extends TestCase {
             }
         }
     }
+    
+    public void test_lexer2() throws Exception {
+        String sql = "SELECT substr('''a''bc',0,3) FROM dual";
+        Lexer lexer = new Lexer(sql);
+        for (;;) {
+            lexer.nextToken();
+            Token tok = lexer.token();
+
+            if (tok == Token.IDENTIFIER) {
+                System.out.println(tok.name() + "\t\t" + lexer.stringVal());
+            } else if (tok == Token.LITERAL_INT) {
+                System.out.println(tok.name() + "\t\t" + lexer.numberString());
+            } else if (tok == Token.LITERAL_CHARS) {
+                System.out.println(tok.name() + "\t\t" + lexer.stringVal());
+            } 
+            else {
+                System.out.println(tok.name() + "\t\t\t" + tok.name);
+            }
+
+            if (tok == Token.EOF) {
+                break;
+            }
+        }
+    }
+    
 }