Add scheme character class helper methods.
Add standalone parseValidScheme, use that in parseScheme.
Add standalone parseValidUsername, parseValidPassword, use that in parseUserInfo.
Add standalone parseValidHostname, use that in parseHostname.
Add standalone parseValidPort, use that in parsePort.
Add standalone parseValidPath, use that in parsePath.
Add standalone parseValidQuery, use that in parseQuery.
Add standalone parseValidFragment, use that in parseFragment.