添加database/DBCritical.h文件
添加database/DBManager.h接口文件
添加database/DBManagerCommon.h文件
add database/DBManagerCommon.cpp
add database/MysqlDBManager.h
add database/MysqlDBManager.cpp
modify Makefile to add -lmysqlclient
add log/server.log to hold the log of server
modified MSNServer, delete database/DBConnectionManager class file