:eq(-x) needs to be updated to reflect 1.8 changes

[ajpiano]

Porting from 12682 in Trac.

Current docs state "Unlike the .eq(index) method, the :eq(index) selector does not accept a negative value for index. For example, while $('li').eq(-1) selects the last li element, $('li:eq(-1)') selects nothing." However according to @dmethvin's comment, this is fixed in 1.8 and :eq and .eq() work the same with negative indices, docs need to be updated to reflect this.

[kswedberg]

Thanks for this, @ajpiano! I think we'll tackle this along with the other 1.8 changes during the summit.

[kswedberg]

Fixed in 4cc3694