Add file "http.c"

Add file "http.c" to parse the HTTP request using the function parsereq.
Use the new type ReqInfo to record the HTTP request.
Can hold 400, 501, 505 .
Can hold simple request.
Can't hold 522:Connection Timed Out status.
Can't hold full request.

BTW, add some exception handling ( malloc(), write(), band())
Merge pull request #9 from lzhang25/master

Add file "http.c", but considering remove some unnecessary memset() later.