In a cargo-driven world the primary location for the name of a crate will be in
its manifest, not in the source file itself. The purpose of this flag is to
reduce required duplication for new cargo projects.
This is a breaking change because the existing --crate-name flag actually
printed the crate name. This flag was renamed to --print-crate-name, and to
maintain consistence, the --crate-file-name flag was renamed to
--print-file-name.
To maintain backwards compatibility, the --crate-file-name flag is still
recognized, but it is deprecated.
[breaking-change]
