Fix up some warnings/errors

[RossSmyth]

Close #791

My process:

1. Add the flags for ignoring the -Weverything errors
2. Go through and remove each flag and attempt to fix them

Not all were successes. Some of the files are laid out in ways I don't really understand.

It is arranged in nice atomic commits, but can be squashed.

Tested with Clang and with GCC.

[mvandervoord]

Hi. Thanks for the collection of fixes! We really appreciate the help!

This project supports more compilers than just clang and gcc, so we need to be a bit careful about some of the changes. If you don't mind making a few tweaks to better support those other compilers?

For example:

• Your direct usage of __attribute__(( blah )) isn't valid. Instead, you should use UNITY_FUNCTION_ATTR()
• Your calls to clang-specific pragma's should be protected by #ifdef __clang__ checks

Thanks so much!

[mvandervoord]

Thanks for the help, @RossSmyth !

[RossSmyth]

I would also recommend #790, #771, and #769 since that is my work account, and I am currently carrying those patches at work.

[RossSmyth]

Thanks!

[mvandervoord]

:) Thank YOU!

I'm not a meson user myself... so I intended to solicit a 2nd opinion on some of those... I'm sure I'll hear about it. ;)