Ucreds

I'm not positive on the `SOCKCREDSIZE()` implementation, but we'll see what CI says I guess.

Removes a compilation warning

Minor fixes for mips-unknown-linux-uclibc

Just adding a few definitions so the toolchain compiles

Add more FreeBSD errnos

Add additional errno constants for NetBSD

Bump to 0.2.34

Use IFF_OACTIVE and IFF_RUNNING even on FreeBSD. Deprecate the DRV ones.

According to @asomers, libc should propagate the use of the portable constants `IFF_OACTIVE` and `IFF_RUNNING` for user-space applications, instead of `IFF_DRV_OACTIVE` and `IFF_DRV_RUNNING`. It least that's my understanding of [his comment](https://github.com/nix-rust/nix/pull/667#discussion_r152396984) in nix-rust/nix#667.

haiku: Add missing lutimes

* BeOS traditionally didn't have lutimes, however to make Haiku
  more compatible and easier to port for, we added an implementation
  of it.

Fix Fuchsia typos

Fix master CI

Apparently the most recently release broke three (!) platforms!

Apparently it fails on 1.23.0 for mysterious reasons

Looks like `cargo test` is now trying to test too many files due to
rust-lang/cargo#4750 so add a clause to the wrapper to ignore the bogus ones for
now

It wasn't expecting a `*.d` file to exist, now it does.

* BeOS traditionally didn't have lutimes, however to make Haiku
  more compatible and easier to port for, we added an implementation
  of it.

Prerequisites to build libc-test on Solaris

These changes are required as a first step to Solaris CI.

With these changes there are no "undeclared"
errors for libc-test on Solaris anymore.

fflags_t is not commonly defined on Solaris or illumos.

futimes is not commonly defined on Solaris, but futimesat is.

Several fixes for DragonFly

With these changes in place, crate "nix" works (with some patches applied).

This was not caught by libc-test, as checks for the execv functions
are disabled.