Fixes preceding underscores and double underscores

[JustCallMeRay]

A good pull request has the following information:

• A reference to a related issue in your repository.

I didn't make one (sorry, I can upon request)

• A description of the changes proposed in the pull request.
  The C++ standard says that anything starting with an underscore is reserved for the standard library and anything containing two underscores is reserved for the compiler. This is only in the global namespace but most of changes are #defines so the difference is moot.

This is rarely an issue but can lead to undefined behaviour being executed on compilers not tested. When it does happen it can be pain to track down.

Please see Jason Turner's video on the subject for more information

• @mentions of the person or team responsible for reviewing proposed changes. ( optional )

[JustCallMeRay]

I did this already