Prevent name clashes with math macros

[jgfoster]

This takes the edits from here and makes them a separate PR.

Fixes #133 (and #165), simplifies #189, and replaces part of #144.

[ianfixes]

I see both a template and a macro definition of max. If both are needed, can you add some code comments explaining that?

[ianfixes]

Oh, I see what's happening: #ifdef __cplusplus wraps the whole section. Can you indent the "body" of both the #ifdef and the #else sections of __cplusplus to make them more evident?

[jgfoster]

Indent added (note that it would be undone by clang-format).

[ianfixes]

I know the formatting isn't standard. There is a lot of c++-side stuff that I'd prefer to keep on the readability side, since this project is still working its way to feature-completeness. Once it works, I'm hoping the larger group of contributors that have joined in will be able to help me take a second look at how it all could be made more solid.

The end goal would be some direct tie-in with the Arduino project itself to enable these sorts of tests in a batteries-included sort of way in the IDE. But that's a long way off, if ever.