Fixed several C++ things
Fixed several C++ things

1. Moved Literal to parser: https://github.com/antlr/grammars-v4/issues/1862
2. Removed LeftShift and RightShift: https://github.com/antlr/grammars-v4/issues/1702
3. Changed Equal to Assign in captureDefault: https://github.com/antlr/grammars-v4/issues/1940
4 Made parameterDeclarationClause optional in lambdaDeclarator: https://github.com/antlr/grammars-v4/issues/1940
5. Added missing Greater in theOperator: https://github.com/antlr/grammars-v4/issues/1702
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