Fix parsing of URLs containing IPv6 addresses

That includes the front-end accepting things like ``[::1]`` and the injector
accepting URLs like ``http://[2001:db8::1]:8080/foo/bar``.

src/client_front_end.cpp

@@ -64,7 +64,7 @@ static ostream& operator<<(ostream& os, const ClientFrontEnd::Task& task) {
 static
 string path_from_url(const string& url) {
     // This is not a bullet-proof URL parser, it just gets some common cases here.
-    static const boost::regex urlrx("^(?:http://[-\\.a-z0-9]+)?(/[^?#]*).*");
+    static const boost::regex urlrx("^(?:http://[-\\.:\\[\\]a-z0-9]+)?(/[^?#]*).*");
     boost::smatch url_match;
     boost::regex_match(url, url_match, urlrx);
     return url_match[1];

src/injector.cpp

@@ -132,7 +132,7 @@ struct InjectorCacheControl {
 
             // Parse the URL to tell HTTP/HTTPS, host, port.
             auto target = rq.target().to_string();
-            static const boost::regex urlrx("^(http|https)://([-\\.a-z0-9]+)(:[0-9]{1,5})?/.*");
+            static const boost::regex urlrx("^(http|https)://([-\\.a-z0-9]+|\\[[:0-9a-fA-F]+\\])(:[0-9]{1,5})?/.*");
             boost::smatch url_match;
             if (!boost::regex_match(target, url_match, urlrx)) {
                 ec = asio::error::operation_not_supported;  // unsupported URL