revset: try to handle hyphenated symbols if lookup callback is available Formerly an expression like "2.4-rc::" was tokenized as 2.4|-|rc|::. This allows dashes in symbols iff the whole symbol-like string can be looked up. Otherwise, it's tokenized as a series of symbols and operators. No attempt is made to accept dashed symbols inside larger symbol-like string, for instance foo-bar or bar-baz inside foo-bar-baz.