removing any calls to `tostring` as a method, in preparation for renaming the method to `_tostring`
initial step in removing `tostring` as a method and renaming it to `_tostring`
bootstrap with `tostring` and `_tostring` support co-equal
removing special support for "tostring" as a method completely
bootstrap using only `_tostring`
fixing up tests to work with syntax changes and `_tostring` changes