
o xmlgrep fanout. print all matching depth paths.
   If match from node N. xmlgrep --fanout n.a
    <n><a i="1"/><a i="2"/><a i="3"/></n>
   result:
     <n><a i="1"/></n>
     <n><a i="2"/></n>
     <n><a i="3"/></n>
   Requires recursing downwards after a match and we want to print result.
   Building of separate nodetree on the side.
   Need to dup tree for each recurse.

o xmlmod refuse to work on incorrect xml.
