fix bug: parse error 'alter table t1 rename to/as t2'

src/main/java/com/alibaba/druid/sql/dialect/mysql/parser/MySqlStatementParser.java

@@ -2296,6 +2296,9 @@ public class MySqlStatementParser extends SQLStatementParser {
                     }
                 } else if (identifierEquals("RENAME")) {
                     lexer.nextToken();
+                    if (lexer.token() == Token.TO || lexer.token() == Token.AS) {
+                        lexer.nextToken();
+                    }
                     MySqlRenameTableStatement renameStmt = new MySqlRenameTableStatement();
                     MySqlRenameTableStatement.Item item = new MySqlRenameTableStatement.Item();
                     item.setName(stmt.getTableSource().getExpr());

src/test/java/com/alibaba/druid/bvt/sql/mysql/MySqlAlterTableTest1.java

@@ -52,5 +52,23 @@ public class MySqlAlterTableTest1 extends TestCase {
         String output = SQLUtils.toMySqlString(stmt);
         Assert.assertEquals("ALTER TABLE t2\n\tADD INDEX (d),\n\tADD UNIQUE INDEX (a)", output);
     }
+    
+    public void test_alter_3() throws Exception {
+        String sql = "ALTER TABLE t1 RENAME TO t2;";
+        MySqlStatementParser parser = new MySqlStatementParser(sql);
+        SQLStatement stmt = parser.parseStatementList().get(0);
+        parser.match(Token.EOF);
+        String output = SQLUtils.toMySqlString(stmt);
+        Assert.assertEquals("RENAME TABLE t1 TO t2", output);
+    }
+    
+    public void test_alter_4() throws Exception {
+        String sql = "ALTER TABLE t1 RENAME AS t2;";
+        MySqlStatementParser parser = new MySqlStatementParser(sql);
+        SQLStatement stmt = parser.parseStatementList().get(0);
+        parser.match(Token.EOF);
+        String output = SQLUtils.toMySqlString(stmt);
+        Assert.assertEquals("RENAME TABLE t1 TO t2", output);
+    }
 
 }