fix for CRM-12404 : 'You do not have permission to execute this url' err...

'You do not have permission to execute this url' this message is shown after hitting url '&q=civicrm/pcp&action=disable' - on frontend side of wordpress during pcp workflow.

This happens because : 
  - Wordpress/civicrm.php contains civicrm_check_permission function which basically allows access only for certain urls for frontend pages visiting.
  - handling for '&q=civicrm/pcp' url wasn't done over here and hence this error.