For coreutils, there are two build artifacts:
1. multicall executable (each utility is a separate static library)
2. individual utilities (still separate library with main wrapper)
To avoid namespace collision, each utility crate is defined as
"uu_{CMD}". The end user only sees the original utility name. This
simplifies build.rs.
Also, the thin wrapper for the main() function is no longer contained in
the crate. It has been separated into a dedicated file. This was
necessary to work around Cargo's need for the crate name attribute to
match the name in the respective Cargo.toml.
Everything in src/common has been moved to src/uucore. This is defined
as a Cargo library, instead of directly included. This gives us
flexibility to make the library an external crate in the future.
Fixes#717.
There are several areas needing improvement:
1) add tests for hard links
2) add implementation for uncommon flags (-d, -L, -n, -P, -r)
3) align error messages more closely with GNU implementation
