ACTION-698 - rules for elements with host language semantics for hidden

Please review section 5.1 [1] and let me know if I got these bullets right
per our discussion last week. In particular,

5.1.1 - last bullet
5.1.2 - new bullet in the MUST NOT and SHOULD NOT lists

[1] http://www.w3.org/WAI/PF/aria-implementation/#include_elements

Andi
                                                                   
                                                                   
                                                                   
  IBM Research       Andi Snow-Weaver                              
                     Accessibility Standards Program Manager       
                     Human Ability & Accessibility Center          
                                                                   
                     Tel: +1-720-663-2789                          
                     Email: andisnow@us.ibm.com