add cmake support
add cmake support
	新文件：    CMakeLists.txt
	新文件：    examples/CMakeLists.txt
	新文件：    examples/chat/CMakeLists.txt
	新文件：    examples/echo/CMakeLists.txt
	新文件：    examples/hello/CMakeLists.txt
	新文件：    gxmpp/CMakeLists.txt
	新文件：    talk/CMakeLists.txt
	新文件：    talk/base/CMakeLists.txt
	新文件：    talk/xmllite/CMakeLists.txt