add log api

src/main/java/com/alibaba/druid/pool/DruidDataSourceStatLogger.java

@@ -17,6 +17,8 @@ package com.alibaba.druid.pool;
 
 import java.util.Properties;
 
+import com.alibaba.druid.support.logging.Log;
+
 /**
  * @author wenshao<szujobs@hotmail.com>
  * @since 0.2.19
@@ -30,4 +32,8 @@ public interface DruidDataSourceStatLogger {
      * @since 0.2.21
      */
     void configFromProperties(Properties properties);
+    
+    void setLogger(Log logger);
+    
+    void setLoggerName(String loggerName);
 }