maint: bump copyright year

Needed to reduce number of 'make syntax-check' failures.

* gnulib: Update to latest.
* bootstrap.conf (src_modules): Add 'assure', to match gnulib module
changes in the meantime.
* .gitignore: Ignore results of assure module.
* cfg.mk (gnulib_dir): Declare our alternate location.
* bootstrap: Regenerate.
* all files: Use 'make update-copyright' to bump year.

Signed-off-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit 102376916e49b6aae85dc6ff0b59699205a74bdf)
[Ultimately, this short-circuits all other commits from other branches
that touched gnulib to any intermediate version]
88 files changed