In mfem::mfem_backtrace, print addresses in hex format.
In mfem::mfem_backtrace, print addresses in hex format.

In mfem::mfem_error, check both MPI_Initialized and MPI_Finalized before
calling MPI_Abort.

mfem/mfem,mfem/mfem,mfem/mfem,kvoronin/mfem-4d-own,mfem/mfem,mfem/mfem,gelever/lamfem