Datepicker - inconsistency on input (fractional) height - position fixed issue

Hi,

To determine the top value for a position fixed datepicker, the input height is needed but 2 different methods (in 2 different places).

1. https://github.com/jquery/jquery-ui/blob/master/ui/widgets/datepicker.js#L778 => use of **offsetHeight**, so we always get an integer (33px for instance).

2. https://github.com/jquery/jquery-ui/blob/master/ui/widgets/datepicker.js#L880 => use of **outerHeight()**, so we may get a fractional number (33.5px for instance).

Result : the check line 886 (https://github.com/jquery/jquery-ui/blob/master/ui/widgets/datepicker.js#L886) may be false in some case and thus the scroll height is not taken into account. The datepicker position is wrong in these cases.

JQuery method **outerHeight()** should be used in both case. What do you think?

Kind regards.