Add rustc-dep-of-std support.

2 jobs for master in 51 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Test
failed #30400
test:default

00:00:51

failed #30401
test:no_std

00:00:50

 
Name Stage Failure
failed
test:no_std Test
cargo 1.32.0-nightly (1fa308820 2018-10-31)
$ cargo test --features no_std
error: failed to parse manifest at `/builds/lygstate/posix-regex/Cargo.toml`

Caused by:
feature `rename-dependency` is required

consider adding `cargo-features = ["rename-dependency"]` to the manifest
ERROR: Job failed: exit code 1
failed
test:default Test
cargo 1.32.0-nightly (1fa308820 2018-10-31)
$ cargo test
error: failed to parse manifest at `/builds/lygstate/posix-regex/Cargo.toml`

Caused by:
feature `rename-dependency` is required

consider adding `cargo-features = ["rename-dependency"]` to the manifest
ERROR: Job failed: exit code 1