Increase Warning Verbosity/Fix Warnings

[cr1901]

Ideally, the code should compile w/ the xc8 equivalent of -Werror, using #pragmas to permit exceptions on a case-by-case basis and with comments explaining why the warning is acceptable.

This includes m-stack, which by default has a number of warnings, but we probably shouldn't touch more than we have to. Use a file-specific compile option to quell m-stack warnings?