add Yaf_Response_Abstract:: setHeader()
optimize code and add Yaf_Response_Abstract:: setAllHeaders()、Yaf_Response_Abstract:: getHeader()
optimize code and add Yaf_Response_Abstract:: clearHeaders()
output headers and response_code where Yaf_Response_Http::response() is called
move setAllHeaders、clearHeaders、getHeader、setHeader to yaf_response_http.c from yaf_response.c
fix some bug and make code better
添加Yaf_Response_Http::resopnse()方法覆盖Yaf_Response_Abstrace::resopnse()，并优化代码
Merge branch 'dev' of https://github.com/wenjun1055/php-yaf

Conflicts:
	tests/070.phpt
	yaf_response.c