Change the way that the ?date= stuff is parsed. It now takes a time (with optional...

Change the way that the ?date= stuff is parsed. It now takes a time (with optional date)
in local time rather than GMT. Note that you are advised to use the date as well as the time
as the time is relative to the current day (which is not much use if the time is in the
future). The date format parsing is pretty strict still:
YYYY-MM-DDTHH:MM:SS   is a format that works. The T is a literal non-digit character. I wouldn't
use a space. The :SS can be omitted. The number of digits *must* be four in the Year.

Originally committed as revision 691 to svn://svn.ffmpeg.org/ffmpeg/trunk