add Neighbor::get_xhold() required by fix ipi bugfixes

src/neighbor.cpp

@@ -2978,6 +2978,14 @@ bigint Neighbor::get_nneigh_half()
   return nneighhalf;
 }
 
+/* ----------------------------------------------------------------------
+ return the pointer containing the last positions stored by the NL builder
+------------------------------------------------------------------------- */
+double **Neighbor::get_xhold()
+{
+  return xhold;
+}
+
 /* ----------------------------------------------------------------------
    add pair of atoms to bondlist array
    will only persist until the next neighbor build

src/neighbor.h

@@ -179,6 +179,7 @@ class Neighbor : protected Pointers {
   double memory_usage();
 
   bigint last_setup_bins;    // step of last neighbor::setup_bins() call
+  double **get_xhold();      // access the latest-computed neighbor list positions
 
  protected:
   int me, nprocs;