Add clasp implementation support

[sdilts]

This makes the tests pass, so it's presumably working correctly.

I think (mp:fence :sequentially-consistent) is correct for the memory barrier, but I'm completely new to the concept.

[ItsMeForLua]

Everything looks good, but give me a couple days to review this PR alongside your other PR so that I can accept both PR's at once. I may instead have you commit the PR to one of the other branches (Ill follow up with another reply in this thread) so we can stage before doing a micro-release in the main branch. But the other branches are a bit messy right now, with some code being updated, and other code being behind the main branch.

And, thank you for your help !

[ItsMeForLua]

This PR is being committed to the develop branch for now until everything is set up fully for a release. Thank you for your help!

[ItsMeForLua]

I want to clarify here that right now, cl-freelock's contributor list does not have you listed, but once I push these commits to the main branch, you'll be listed as a contributor. Just wanted to clarify this so that there isn't any confusion.