conf: Add new domain XML element 'iothreadids'
    
    Adding a new XML element 'iothreadids' in order to allow defining
    specific IOThread ID's rather than relying on the algorithm to assign
    IOThread ID's starting at 1 and incrementing to iothreads count.
    
    This will allow future patches to be able to add new IOThreads by
    a specific iothread_id and of course delete any exisiting IOThread.
    
    Each iothreadids element will have 'n' <iothread> children elements
    which will have attribute "id".  The "id" will allow for definition
    of any "valid" (eg > 0) iothread_id value.
    
    On input, if any <iothreadids> <iothread>'s are provided, they will
    be marked so that we only print out what we read in.
    
    On input, if no <iothreadids> are provided, the PostParse code will
    self generate a list of ID's starting at 1 and going to the number
    of iothreads defined for the domain (just like the current algorithm
    numbering scheme).  A future patch will rework the existing algorithm
    to make use of the iothreadids list.
    
    On output, only print out the <iothreadids> if they were read in.