HTTP response splitting via unfiltered CRLF

CRLF injection in cpp-httplib 0.5.8 and earlier allows remote attackers to split HTTP responses with crafted header values. Response::set_header stores supplied names and values unchanged, and Response::set_redirect forwards its URL to that setter; write_headers then serializes embedded CRLF bytes as new header lines. The flaw is reachable only when an application passes attacker-controlled data into either setter, allowing response-header injection such as an attacker-chosen Set-Cookie field.