hdf5

[svn-r12209] Purpose:
Bug fix.

Description:
getenv_all would fail if one calls it without calling MPI_initialized first.
This may happen if one uses PHDF5 library to build a serial nature code
and does not make any MPI calls.

Solution:
Added code to detect if MPI has been initialized. If not, use the
original getenv.

Platforms tested:
heping (serial) and mir (parallel).