combobox/filtering select: current item not indicated in the dropdown list when in high contrast mode

[Becky Gibson]

The current item (which is highlighted in the dropdown list of choices in standard mode) is always displayed in the textbox so technically this meets a11y requirements. But, it would greatly improve the usability if the current item was indicated in the dropdown list when in high contrast mode. This could be accomplished via a border (although that might change the size) or perhaps by underline.

[Becky Gibson]

I marked this a 1.0 in case it is an easy fix but can be moved to 1.1 if necessary.

[Becky Gibson]

(In [10936]) fixes #4767 no indication of current item in combobox drop down. fixed by adding .dijit_a11y .dijitMenuItemHover to draw dotted border.