slingshot: sync with upstream, and simplify accordingly.

* slingshot: Sync with upstream.
* bootstrap: Update from slingshot.
* bootstrap.slingshot: Remove.  No longer required.
* bootstrap.conf: Remove bootstrap.slingshot boilerplate.
(func_ensure_changelog, specl_force_readme): Remove. Automated by
slingshot now.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
maint: update copyright notices to include 2014.

* .x-update-copyright: New file. Exclude files not owned by this
project from update-copyright rules.
* bootstrap.conf (slingshot_files): Add update-copyright.
* .gitignore: Update accordingly.
* local.mk (update_copyright_env): Settings for update-copyright.
* bootstrap.conf, build-aux/larch, configure.ac,
lib/larch/from.lua, lib/main.lua, lib/specl.lua,
lib/specl/color.lua, lib/specl/formatter/progress.lua,
lib/specl/formatter/report.lua, lib/specl/loader.lua,
lib/specl/matchers.lua, lib/specl/optparse.lua,
lib/specl/shell.lua, lib/specl/util.lua, local.mk,
specs/specs.mk: Bump copyright year.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>