RFC 6455 compliance
RFC 6455 compliance

Treats the |Upgrade| header field as a case-insensitive value. See https://tools.ietf.org/html/rfc6455#section-4.2.1
This fixes compatibility with Apache httpd when using mod_proxy_wstunnel. See https://github.com/apache/httpd/blob/e1384a888c84d725d676bbda20d9020f413553cd/modules/proxy/mod_proxy_wstunnel.c#L329

Kilobyte22/webrick-websocket