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.
(binary:application/octet-stream)