Add AF_ALG constants and structures

This reverts commit ae2663a7.

Moved inotify declarations up so that it works on android too.

Following my previous pull request to include inotify bindings, I would like to move the code so that it benefits android too.

Moved inotify_rm_watch out of the generic notbsd target and into specific linux and android targets because the second argument has a different type in android and linux.

Broader sendmmsg() / recvmmsg() support

As a prerequisite for getting `sendmmsg()` / `recvmmsg()` into nix ( https://github.com/nix-rust/nix/pull/1017 ), support for non-linux platforms needs to be added in libc.

The initial commits in this PR will just be to test out target support via CI.

Add IP_ORIGDSTADDR and others on FreeBSD.

A follow-up from #1252.

CC @asomers.

r? @gnzlbg

Add missing group entry functions for Solaris/Illumos

This commit adds definitions for `setgrent`, `endgrent`, and `getgrent` which were missing (but available for FreeBSD and other *nix systems).

Allow installing rustfmt component to fail