allow ^ in URLs

Users may select specific outputs using the ^output syntax or selecting
any output using ^*.

URL parsing currently doesn't support these kinds of output references:
parsing will fail.

Currently `queryRegex` was reused for URL fragments, which didn't
include support for ^. Now queryRegex has been split from fragmentRegex,
where only the fragmentRegex supports ^.

src/libutil/url.cc

@@ -15,7 +15,7 @@ ParsedURL parseURL(const std::string & url)
         "((" + schemeRegex + "):"
         + "(?:(?://(" + authorityRegex + ")(" + absPathRegex + "))|(/?" + pathRegex + ")))"
         + "(?:\\?(" + queryRegex + "))?"
-        + "(?:#(" + queryRegex + "))?",
+        + "(?:#(" + fragmentRegex + "))?",
         std::regex::ECMAScript);
 
     std::smatch match;