Auto merge of #27762 - alexcrichton:fix-libc, r=aturon
Auto merge of #27762 - alexcrichton:fix-libc, r=aturon

The corrected signature of `ioctl` broke some crates on crates.io, and it's not
currently worth the major version bump of libc, so for now keep the old
signature around for crates.io builds only with a comment to remove it at a
future date.

This should allow libc on crates.io to update to the master version in-tree.
I've verified that this was the only breakage of substance between the version
libc is currently built with and today's master branch.

dwillmer/rust,graydon/rust,GBGamer/rust,graydon/rust,graydon/rust,dwillmer/rust,GBGamer/rust,GBGamer/rust,dwillmer/rust,dwillmer/rust,aidancully/rust,GBGamer/rust,dwillmer/rust,graydon/rust,GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,GBGamer/rust,aidancully/rust,dwillmer/rust,GBGamer/rust,dwillmer/rust,GBGamer/rust,aidancully/rust,dwillmer/rust,aidancully/rust