maint: update copyright notices to include 2014.

* .x-upate-copyright: New file. Exclude files not owned by this
project from update-copyright rules.
* local.mk (update_copyright_env): Set appropriately.
* configure.ac, ext/yaml/emitter.c, ext/yaml/lyaml.h,
ext/yaml/parser.c, ext/yaml/scanner.c, ext/yaml/yaml.c,
lib/lyaml.lua, local.mk: Bump copyright year.
* .gitignore: Update.

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