fix #1349 aria.utils.dragdrop.Drag on Chrome with elements in position:fixed

This commit fixes a problem inside the getOffset method of the aria.utils.Dom class. We use the offsetParent property to compute the element position, but for a fixed element in Chrome the offsetParent is null and it breaks the code.
fix #1360 ButtonVerticalAlignTestSuite

Allowing tests from ButtonVerticalAlignTestSuite to pass for other skins
than atskin and atflatskin.
fix #1361 Fixing Robot tests failures on Firefox 3.x

Robot tests are supposed to be ignored on Firefox 3.x, however, there
were still indirect errors after commit e55822502a93ba95fdcf3b07f885d543c99692c0.
fix test.aria.widgets.errorlist.ListErrorTestCase was broken

IE7, IE8 and Firefox 3 return the HTML content in different ways, with more or less processing applied to the string. All content express the same thing, but are not formatted identically.

This fixes the test by avoiding some special cases and by having a more loose comparison algorithm.

Fixes tests introduced by #1357
Closes #1362
fix Select loses focus state when an item is selected