Fix in dcd reader to allow reading of dcd files written by namd 2.11

We cannot rely on the header containing the number of frames in the
dcd files, as namd 2.11 sets this variable to 0.

modules/io/src/mol/dcd_io.cc

@@ -279,7 +279,7 @@ mol::CoordGroupHandle load_dcd(const mol::AtomHandleList& alist, // this atom li
   geom::Vec3 cell_size, cell_angles;
   size_t frame_size=calc_frame_size(ucell_flag, gap_flag, xlist.size());
   int i=0;
-  for(;i<header.num;i+=stride) {
+  while(true){
     if (!read_frame(istream, header, frame_size, ucell_flag, gap_flag, 
                     swap_flag, xlist, clist, i,cell_size,cell_angles)) {
       break;
@@ -292,11 +292,12 @@ mol::CoordGroupHandle load_dcd(const mol::AtomHandleList& alist, // this atom li
 
     // skip frames (defined by stride)
     if(stride>1) istream.seekg(frame_size*(stride-1),std::ios_base::cur);
-  }
-  istream.get();
-  if(!istream.eof()) {
-    LOG_VERBOSE("LoadCHARMMTraj: unexpected trailing file data, bytes read: " 
-                 << istream.tellg());
+    i+=stride;
+    istream.get();
+    if(istream.eof()){
+      break;
+    }
+    istream.unget();
   }
 
   LOG_VERBOSE("Loaded " << cg.GetFrameCount() << " frames with "