configure: update version to 2.1.3

configure: update version to 2.1.2

configure: update version to 2.1.1

configure: update version to 2.1.0

eventloop: use 'deadline' instead of 'time_min' in various places

'deadline' is a more descriptive term, since the event scheduler implements earliest-deadline-first
scheduling, and 'time_min' was the deadline that had to be met.

libmowgli 2.0.0-beta1.

libmowgli 2.0.0-alpha1.