bitflags 1.3.0 breaks nix

[taiki-e]

#187 breaks nix because it does not respect existing repr attributes.

error[E0692]: transparent struct cannot have other repr hints
  --> /home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/nix-0.22.0/src/sys/statvfs.rs:15:12
   |
13 | / libc_bitflags!(
14 | |     /// File system mount Flags
15 | |     #[repr(C)]
   | |            ^
16 | |     #[derive(Default)]
...  |
52 | |     }
53 | | );
   | |__^
   |
   = note: this error originates in the macro `::bitflags::bitflags` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0692`.

cc @flier @KodrAus

[KodrAus]

I knew the first one of these couldn't be far off...

[KodrAus]

I think we should revert the automatic addition of #[repr(transparent)] and just leave it up to callers to add whatever repr they need.

In the meantime I'll yank 1.3.0

[KodrAus]

Yanked