Issue with command unfix for the fix bd baoab

[c-ruscher]

I had some issue (segmentation fault) when trying to use the unfix command on the fix bd baoab.
It seems to come from the fact that the memory associated to the quantity rnum cannot be freed.

I managed to solve the issue by adding to the cpp:

FixBDBAOAB::~FixBDBAOAB()
{
  delete random;
  memory->destroy(rnum);
  atom->delete_callback(id,0);
}

In the header file I also changedvirtual ~FixBDBAOAB() {} to virtual ~FixBDBAOAB()