Disabled search spacing

1. Check that on this site, the search input is left-aligned, and the auxiliary links are right-aligned.

2. Add search_enabled: false to _config.yml, then rebuild.

3. Check that the search input is no longer displayed, and the auxiliary links are still right-aligned.

However, the alignment of the custom header contents is inconsistent when the search input and/or the aux links are displayed (also when neither is displayed). See issue #1003.