Modified timerender.js absolute_time() to include the year
in the returned string when the supplied timestamp is in
an older year. This included adding an optional second
argument to specify the current date to facilitate unit
tests.
Fixes#5737.
Having get_full_time produce a date string non-compliant with RFC2822 or
ISO 8601 caused problems when showing edition timestamps on a message's
edit history.
Now it returns an ISO 8601 date string (1978-10-31T13:37:42Z).
The floating_recipient_bar is cloned from recipient_bar elements.
The cloning created elements in the DOM with duplicate id
attributes, specifically <span id="timerender{id}">, which
contains the date of the message stream. The timerender span
will now use class="timerender{id}" instead.
Fixes#4997.
Fixes#5128.
timerender.js render_now() will always include older
years when rendering the date stamp on the recipient bar
and the date rows above messages.
Fixes#4843.