Add missing string-to-number functions from ISO C

[LegionMammal978]

These should be the observable API changes:

• ISO C90 function atol() is added to all fuchsia, unix, vxworks, wasi, and windows targets.
• ISO C90 function atof() is added to android, redox, and vxworks.
• ISO C99 functions atoll(), strtoll(), and strtoull() are added to all fuchsia, unix, vxworks, wasi, and windows targets.

Also, I wasn't exactly sure where to insert the new functions, so I just tried to place them near related functions.

[rustbot]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @JohnTitor (or someone else) soon.

Please see the contribution instructions for more information.

[rustbot]

Some changes occurred in solarish module

cc @jclulow, @pfmooney

[JohnTitor]

Do you really want to use all of the items? The huge addition makes review harder and may cause unneeded breaking change (if upstream changes ABI, it would introduce a breaking change here. It'd be troublesome when there's no real user but we have to think about the effect of that breaking change).
Also, changing the clock_t type is a breaking change and this PR cannot be merged until we (maintainers) figure out how to set the release policy and ship breaking changes, so I'd recommend dropping the changes that you don't need and separating diff into some PRs.

[LegionMammal978]

Alright, I've scaled this PR back to just the string-to-number functions, since those were what I was originally missing.

[JohnTitor]

Great, thanks! @bors r+

[bors]

📌 Commit 6a58758 has been approved by JohnTitor

It is now in the queue for this repository.

[bors]

⌛ Testing commit 6a58758 with merge 07636f6...

[bors]

☀️ Test successful - checks-actions, checks-cirrus-freebsd-12, checks-cirrus-freebsd-13, checks-cirrus-freebsd-14
Approved by: JohnTitor
Pushing 07636f6 to master...