[mpi-21] Fix MPI-2 C++ "static const" statement

["Jeff Squyres" <jsquyres@xxxxxxxxx>]

In the current MPI 2.0 document, MPI-2:2.5, p9:17-18 states:

"MPI provides certain predefeined opaque objects and predefined,
static handles to these objects.  The user must not free such objects.
 In C++, this is enforced by declaring the handles to these predefined
objects to be {\tt static const}."

The "static" in the last sentence should be deleted.  When using
namespaces, all the MPI symbols are in the namespace and objects do
not need to be static in a singleton object for the MPI class.

Specifically: they are static *only* if you are using the singleton
object for the MPI class.  The context for the statement is talking
about the constant quality; the "static" is superfluous -- describing
whether "static" is necessary or not would be too much for this
section.

-- 
{+} Jeff Squyres