v2.5.0-test

Full Changelog: v2.4.0...v2.5.0

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Add GLR parser generator

Adding %glr; directive will switch the parser generation to GLR parser.
With this directive, any Shift/Reduce, Reduce/Reduce conflicts will not be treated as errors.

Resolving Ambiguities

You can resolve the ambiguties through the reduce action.
Simply, returning Result::Err(Error) from the reduce action will revoke current path.

Note on GLR Parser

• Still in development, not have been tested enough (patches are welcome!).
• Since there are multiple paths, the reduce action can be called multiple times, even if the result will be thrown away in the future.
  • Every RuleType and Term must implement Clone trait.
• User must be aware of the point where shift/reduce or reduce/reduce conflicts occur.
  Every time the parser diverges, the calculation cost will increase.

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Add lookahead predefined variable in reduce action

You can refer via lookahead variable in the reduce action, which token caused the reduce action.

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