Merge branch 'newer-rust-version' into 'master'

.gitlab-ci.yml

Cargo.toml

Makefile

README.md

src/lib/builtins/command_info.rs

src/lib/builtins/exec.rs

src/lib/builtins/exists.rs

src/lib/builtins/functions.rs

src/lib/builtins/is.rs

src/lib/builtins/job_control.rs

src/lib/builtins/mod.rs

src/lib/builtins/set.rs

src/lib/builtins/source.rs

src/lib/builtins/status.rs

src/lib/builtins/variables.rs

src/lib/lib.rs

src/lib/parser/assignments/actions.rs

src/lib/parser/assignments/checker.rs

src/lib/parser/loops.rs

src/lib/parser/pipelines/collector.rs