odd assert failure

[Bill Janssen]

Am I correct in believing that if I hit this branch in
SimulationRuntime/c/simulation/simulation_info_xml.c, that I've found a
bug?  If so, I'll report it with the model that triggers it.

    if (curIndex != ix) {
      THROW4("%s: Info XML %s got equation with index %ld, expected %ld", 
__FILE__, xml->fileName, ix, curIndex);
    }

Bill