These patches build toward adding the current latest release
(0.9.6) of ripgrep-all  to rust-apps.scm.
There were numerous occasions where I was adding versions of Rust
libraries between two existing versions of the same library. In
those cases, I left all other versions untouched. I'm not sure if
this is the correct approach since it looks like we try to inherit
from the version that immediately precedes in the scm file.