get rid of warning about non-virtual destructors

the tracers class is apparently annoying the compiler, but I added the
"final" specifier, and I no longer get warnings. hopefully the code is
sane.

bfps/cpp/base.hpp

@@ -36,10 +36,15 @@ inline int MOD(int a, int n)
 }
 
 #ifdef OMPI_MPI_H
+
 #define BFPS_MPICXX_DOUBLE_COMPLEX MPI_DOUBLE_COMPLEX
+
 #else
+
 #define BFPS_MPICXX_DOUBLE_COMPLEX MPI_C_DOUBLE_COMPLEX
-#endif
+
+#endif//OMPI_MPI_H
+
 
 #ifndef NDEBUG
 

bfps/cpp/tracers.hpp

@@ -29,7 +29,7 @@
 extern int myrank, nprocs;
 
 template <class rnumber>
-class tracers:public slab_field_particles<rnumber>
+class tracers final:public slab_field_particles<rnumber>
 {
     public:
         rnumber *source_data;