bug#23419: 25.0.93; double-click-time

[martin rudalics]

The documentation of ‘double-click-time’ is as:

  Maximum time between mouse clicks to make a double-click.
  Measured in milliseconds.  The value nil means disable double-click
  recognition; t means double-clicks have no time limit and are detected
  by position only.

However, most uses of ‘double-click-time’ in the lisp directory silently
assume that the value is a number which typically fails in ‘sit-for’s
like, for example, in help.el's

  (not (sit-for (/ double-click-time 1000.0) t))

when ‘double-click-time’ is either t or nil.

Could someone out there who understands the semantics of these
‘sit-for’s please fix them.  I can eventually do that myself but these
semantics are yet pretty unclear to me.

TIA, martin