add apis for consistent handling of tabindex

[becky]

the tabindex attribute is treated differently by the browser and between HTML and XTML. We should add apis for getting and setting tabindex attribute to avoid bugs due to these differences.

[becky]

See http://www.weba11y.com/blog/2007/11/29/fun-with-the-tabindex-attribute/ for details about tabindex

I think we should have the following apis:

setTabindex(element, value) {element.tabIndex = value;}

getTabindex(element) { element.getAttribute(tabindex); }

hasTabindex(element) { element.hasAttribute(tabindex); //needs work for IE }

We also need to be consistent in templates and always specify with lowercase letter i (eye) (although tabindex is generally not in the templates any longer)

[simonjb]

(In [11891]) Added new API for getting and setting HTML attributes: dojo.hasAttr(), dojo.attr(), and dojo.removeAttr(). Fixes #5055. !strict (errors outside of my changes)

[simonjb]

(In [11892]) Minor doc fix. Refs #5055. !strict

[peller]

We need to confirm that this belongs in _base.

[simonjb]

(In [11895]) Fixed up the _base/html.html unit test file to pass on Opera 9. I disabled some tests that cannot pass (tabindex="-1"). Refs #5055.

[simonjb]

(In [11981]) Small code simplification for dojo.hasAttr(). Refs #5055. !strict

[simonjb]

In December I wrote up a post to the Dojo contributors mailing list examining the size impact of the API:

http://dojotoolkit.org/pipermail/dojo-contributors/2007-December/008530.html

I received only one response, which asked that the code be made smaller but stay in _base (http://dojotoolkit.org/pipermail/dojo-contributors/2007-December/008531.html). I have made some small size reductions and I think I will close this ticket, leaving the API in _base.

If we want to look again at moving it before 1.1 we could open a new ticket.