Update ptr::copy_nonoverlapping

[usbalbin]

Update ptr::copy_nonoverlapping with feature gate and link to tracking issue.

[usbalbin]

I have not quite figured out how to compile, I am currently getting

$ mdbook build
2021-01-04 19:57:22 [INFO] (mdbook::book): Book building has started
Warning: The mdbook-mermaid preprocessor was built against version 0.3.7 of mdbook, but we're being called from version 0.4.4
2021-01-04 19:57:22 [INFO] (mdbook::book): Running the html backend
2021-01-04 19:57:22 [ERROR] (mdbook::utils): Error: Rendering failed
2021-01-04 19:57:22 [ERROR] (mdbook::utils):    Caused By: Unable to copy across additional CSS and JS
2021-01-04 19:57:22 [ERROR] (mdbook::utils):    Caused By: Unable to copy /home/albin/rust/const-eval/skill-tree.css to /home/albin/rust/const-eval/book/skill-tree.css
2021-01-04 19:57:22 [ERROR] (mdbook::utils):    Caused By: No such file or directory (os error 2)

so my changes are not tested at all(!)

[oli-obk]

Heh, yea, that failure is because the skill tree mdbook thing needs some initial setup. We haven't really documented anything, but in CI this is

const-eval/.github/workflows/deploy_skill_tree.yml

Line 32 in 7f22c4b

run: mdbook-skill-tree install

(you need to install that command first)

[oli-obk]

The change lgtm tho, so let's just make this CI's job so you don't have to install anything

[usbalbin]

Ok, thanks :)