Smart description tooltips disabled when element's #disabled attribute is set to FALSE

Problem/Motivation

When using the "Smart form descriptions (via Tooltips)" feature, if an element's '#disabled' attribute is set to FALSE (e.g. through hook_form_alter), the tooltip on that element is disabled. This is due to a bug in includes/common.inc, line 86:

 // Ignore if the target element is #disabled.
 || isset($target['#disabled'])

Bootstrap treats any element where the '#disabled' attribute exists as a disabled element, regardless of the value of that attribute.

According to the D7 Form API reference, FALSE is a valid value here. Bootstrap shouldn't disable the tooltip if the '#disabled' attribute is set to FALSE.

Steps to reproduce

1. In the Bootstrap theme settings , enable JavaScript tooltips and "Smart form descriptions (via Tooltips)". (These should be enabled by default.)
2. Use the following code in a custom module file replicate this bug on the default login form, which should have descriptions on both the Username and Password fields:
   

   function MYMODULE_form_user_login_alter(&$form, &$form_state, $form_id){
     $form['name']['#disabled'] = FALSE;
   }

3. Observe that on the Username field, the tooltip is disabled and the field's description is printed beneath the field, as if the tooltip were disabled via '#smart_description' => FALSE. The Password field, which has not been changed, should render the tooltip as expected.

Proposed resolution

In includes/common.inc, check the value of $target['#disabled'] before disabling tooltips on that field. (See patch below.)