* Move the shellcheck script from the Makefile to its own script file
* Reformat the shellcheck script so it's easier to read and modify
* Call the shellcheck script from the pre-commit hook
Fixes bug 30967; not in any released version of Tor.
The pre-push hook already calls the pre-commit hook, which calls
practracker.
Also update the script comments to avoid similar issues in future.
Fixes bug 31462; bugfix on 0.4.1.1-alpha.