MockHTMLSelectElement and MockHTMLOptionElement should behave like real browser inputs

[Jonathan Jacobs]

Javascript 1.5 supports getter and setter properties[1][2], which can be used to implement "value" properties for MockHTMLOptionElement and MockHTMLSelectElement that behave more like their web browser counterparts. This will also provide an opportunity to uncomment a test in Methanal.Tests.TestView.TestSelectInput.

[1] <http://ejohn.org/blog/javascript-getters-and-setters/>
[2] <http://whereswalden.com/2010/04/16/more-spidermonkey-changes-ancient-esoteric-very-rarely-used-syntax-for-creating-getters-and-setters-is-being-removed/>