message: drake.cxx: Add 'ipp' to the list of known Header extensions.
diff: @@ -1626,6 +1626,7 @@ class Header(Node):
  Node.extensions['h'] = Header
  Node.extensions['hh'] = Header
  Node.extensions['hpp'] = Header
  +Node.extensions['ipp'] = Header
  Node.extensions['hxx'] = Header
  class ResourceFile(Node):
  