For routing a request, the URL without the query string
is usually required. The method http_request_path() returns
the path component of the URL (i.e. everything befor the
first "?") and the method http_request_querystring() returns
the query string components of the URL (i.e. everything
after the first "?").

The method http_request_query() returns the value of a given
key in the query. The method http_request_iterate_query()
iterates over all query keys.

if the  grwprintf_t capacity is to small and the first snprintf failed do not count the first (snprintf) bytes as written

When writing the answer to an HTTP request into the socket, the write might have to proceed in multiple parts. (E.g. if the receiver is not able to receive the data fast enough.) To deal with this situation, the server continues execution after a partial write, but changes the flag on the request's epoll object to trigger once the request's socket becomes writable again. However, once the response is fully written, the flags are not changed back, so that subsequent requests (for a keep-alive connection) do not trigger epoll, resulting in the server missing requests.

Fix broken connection after interrupted write.

fix a nasty bug of _grwprintf()

# Conflicts:
#	httpserver.h

~ bugfixes grwprintf_t siz