Fixes #10674: Form controls in disabled fieldset legend

[mdo]

This undoes the disabling of all form controls for those within the first legend in a disabled fieldset. It's a gnarly selector, and doesn't work for IE8, so I'll need to add a note to the docs, but it does the trick. See it in action: http://jsfiddle.net/tyVF4/3/.

/cc @darobin @cvrebert

[cvrebert]

This doesn't deal with buttons... Fixing them would probably require super-gnarly stuff; not fixing them would be an annoying inconsistency.

[cvrebert]

Also, are we sure that the relevant selector is first-of-type and not first-child? I admit the standardese isn't crystal clear on this.

[mdo]

I think it means first of type based on my reading of the spec. That said, we can noodle on this for v3.1, so not a rush right now. We can figure it out next week or so.

[mdo]

Just pushed a big update on this that should have all buttons in a disabled fieldset working fine, just like the inputs within that first fieldsets legend. See http://jsbin.com/usayeRU/3/.

This removes all the default disabled styles we applied to buttons—they're only there for IE8 and maybe IE9. That said, removing them made it super easy to re-enable the button. So, given it fubars IE to some degree, I don't think we can do this until v4 maybe.

Closing out with the full context until then.