tooltipdialog above dropdownbutton does not display correct

[liucougar]

see the connector in the screenshot

this only affects IE 6 (did not try IE 7 though), while FF is ok

[liucougar]

there is a gap between the connector and the main body of the tooltipdialog

[liucougar]

How to reproduce:

• in IE, load dijit/tests/test_Dialog.html
• scroll down the page, until the button "Show Tooltip Dialog pointing upwards, with links" is shown at the bottom of the viewport
• click on the button

[bill]

(In [9919]) Fix a bunch of layout problems with Tooltip/TooltipDialog?. In short

• don't use margin with elements overflowing their containing block; too unstable.
• tooltip appears differently depending on it's position, and even it's size changes, so add callback to position code to set orientation before querying the size.

Fixes #3826 Note that tooltips on Safari seem broken before and after this change, needs to be looked into separately.

[bill]

(In [9922]) Check if orient() is defined or not. Refs #3826.