The idea is to defend against some adversary-in-the-middle attacks.
Also prefer git.savannah.gnu.org over its shorter alias, git.sv.gnu.org
to avoid a warning e.g., from git clone.
Also, drop any final ".git" suffix on the resulting URIs.
Inspired by Paul Eggert's nearly identical changes to coreutils.
Run "make update-copyright" and then...
* gnulib: Update to latest with copyright year adjusted.
* tests/init.sh: Sync with gnulib to pick up copyright year.
* bootstrap: Likewise.
Run "make update-copyright" and then...
* gnulib: Update to latest with copyright year adjusted.
* tests/init.sh: Sync with gnulib to pick up copyright year.
* bootstrap: Likewise.