Compatibility broken with rust 1.41

[jeroen]

Not sure if this is considered important, otherwise feel free to close!

As of commit c27d7c5 this crate no longer compiles with the stock rustc 1.41 on the latest Debian releases. The compilation fails when compiling object-0.23.0.

error[E0658]: subslice patterns are unstable
   --> /tmp/Rtmp90SLnd/R.INSTALL204d8c202e2/gifski/src/.cargo/registry/src/github.com-1ecc6299db9ec823/object-0.23.0/src/read/mod.rs:162:41
    |
162 |             [0x7f, b'E', b'L', b'F', 1, ..] => FileKind::Elf32,
    |                                         ^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/62254

error[E0658]: subslice patterns are unstable
   --> /tmp/Rtmp90SLnd/R.INSTALL204d8c202e2/gifski/src/.cargo/registry/src/github.com-1ecc6299db9ec823/object-0.23.0/src/read/mod.rs:164:41
    |
164 |             [0x7f, b'E', b'L', b'F', 2, ..] => FileKind::Elf64,
    |                                         ^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/62254

error[E0658]: subslice patterns are unstable
   --> /tmp/Rtmp90SLnd/R.INSTALL204d8c202e2/gifski/src/.cargo/registry/src/github.com-1ecc6299db9ec823/object-0.23.0/src/read/mod.rs:166:38
    |
166 |             [0xfe, 0xed, 0xfa, 0xce, ..]
    |                                      ^^
    |
    = note: for more information, see https://github.com/rust-lang/rust/issues/62254

This had caught me a bit by surprise, and I had to do a hotfix release of my application to downgrade to backtrace 0.3.55 in order for it to work on Debian.

[philipc]

I'm not a maintainer for this crate, but I think that's fine, I was just surprised because your other comment said 1.43.1. See #211 (comment) regarding minimum rust version for this crate.

[alexcrichton]

Thanks for the report, but this isn't considered a breaking change for this crate, so I'm going to close.