main.c v1.05, net.c v1.15, http.c v1.05 (logging & response head)

Add response head:
Date
Server
Last-Modiﬁed
Content-Type
Content-Length

Add logging:
format: ’%a %t "%r" %>s %b’
%a The remote IP address.
%t The time the request was received (in GMT).
%r The (quoted) first line of the request.
%>s The status of the request.
%b Size of the response in bytes. Ie, "Content-Length"