Remove warnings for underscored protocol definition arguments?

[OvermindDL1]

Underscored protocol definition arguments is probably a bug in any case, but it might still be useful at times, perhaps should remove the warning from them?

[OvermindDL1]

Thought was spurred by #4.

[jjl]

Is this still relevant after least week's arguments mangling patch?

[OvermindDL1]

Although underscores in fallbacks are fixed, there are still some corner cases with underscores and implementations that I might want to look at (specifically with macro's and inlines).