configury: go back to SteveDonovan master LDoc now that it works.

* bootstrap.conf (buildreq): Replace gvvaughan/next-1 build of
LDoc with upstream master (1.4.0 to be).

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
zmacs: don't require removed zile.registers module.

Forgot to remove these in changeset e6e89ee.
* bin/zmacs: Remove `require "zile.registers"`.
* bin/zz: Likewise.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>
travis: simplify custom travis build script.

* travis.yml.in: Merge improvements from slingshot, and simplify.
* .travis.yml: Regenerate.

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