Double-check next timeout when adding events

When resuming the system from a suspended state, the ev_timeout field
of a scheduled timer event may be in the past. This leads to
unexpected behavior when scheduling a short-duration timer event
immediately after returning from suspension, because the new event
does not land on top of the timeout minheap and so the event loop
(blocked on a possibly long-duration timeout) is not notified.

This patch checks for this condition and, if it obtains, notifies the
event loop.
Change maintainer to me
Make --disable-libevent-regress work again
build test/test-script.sh on systems with a less-featureful $<
Add new callback for "internal" http request errors - error_cb.

It is useful to know why you callback called with NULL (i.e. it failed),
for example if you set max_body with evhttp_connection_set_max_body_size()
you must know that it failed because of body was longer than this size.
Merge remote-tracking branch 'github-azat-non-deb/pass-http-client-error-codes-to-callback' into 2.1-testing
Fix arguments number for evhttp_request_set_error_cb()

There was one unused and not needable - cbarg
Merge remote-tracking branch 'github-azat-non-deb/pass-http-client-error-codes-to-callback' into 2.1-testing