When use-ipv6 is enabled, make mariadb publish an url of the form:
  `mysql://user:password@[ipv6]:port/database`

instead of:
  `mysql://user:password@ipv6:port/database`

which results in the zope instances crashing during processing
due to urlparse.urlsplit failing to parse the url.

Make it possible to mock any specific cron entry.

Those are candidates to be shared by some other place, like slapos testing.

See merge request nexedi/slapos!1693

Following advice from https://luajit.org/download.html use recent commit id,
but rely on github archive.

Drop obsoleted patch, enforce --with-shared-termcap-library

Also use directly archive with patches.

Changes:
 * use xz archive
 * stabilize patch name
 * update patch to current version