add a warning if the bonded cutoff is large

This should print a warning when 2x the bonded interaction cutoff list larger then other cutoffs, as was the setting before the performance optimization with the change in https://github.com/lammps/lammps/pull/758/commits/269007540569589aa7c81d9ba1a4b93d34b8c95d

src/USER-REAXC/pair_reaxc.cpp

@@ -388,7 +388,10 @@ void PairReaxC::init_style( )
   neighbor->requests[irequest]->ghost = 1;
 
   cutmax = MAX3(control->nonb_cut, control->hbond_cut, control->bond_cut);
-
+  if ((cutmax < 2.0*control->bond_cut) && (comm->me == 0))
+    error->warning(FLERR,"Total cutoff < 2*bond cutoff. May need to use an "
+		   "increased neighbor list skin.");
+		   
   for( int i = 0; i < LIST_N; ++i )
     lists[i].allocated = 0;