Do not force --all for instance in order to test real instantiation.

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 !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