Cleanup tasks list for our old Macro Guidelines

[felix91gr]

There are a handful of errors in our Macros chapter. Here's an attempt at listing them all in an actionable way.

1. The issues in this list may be incomplete. Please help me figure out all the changes that need to be done, if you find that some are missing!
2. There's a discussion thread in the wg-macros Zulip channel, where some folks have helped a lot in figuring this list out.

This is the task list. Each item has its own Issue, to help keep the discussions easier to follow.

• Attribute Macros shall not be used
• Procedural Macros shall not be used
• Shall ensure complete hygiene of macros
• Blanket forbiddance of macro usage

NOTE: this issue is a WIP. I'm still adding the items!

[felix91gr]

Thanks to @theemathas once again for bringing these up to my attention. When I first read them, I decided to work on revising the Macro rules, but I had forgotten about it :)