These two macros set the MCA prefix and MCA cmd line id,
respectively. Specifically, MCA parameters will be named
PREFIX<foo> in the environment, and the cmd line will use
-ID foo bar.
These macros must be called during configure.ac and a value
supplied. In the case of Open MPI, the values given are
PREFIX=OMPI_MCA_ and ID=mca.
Other projects (such as ORCM) will call these macros with
their own unique values. For example, ORCM uses PREFIX=ORCM_MCA_
and ID=omca
This scheme is necessary to allow running Open MPI applications under
systems that use their own versions of ORTE and OPAL. For example,
when running OMPI applications under ORCM, we need the MCA params passed
to the ORCM daemons to be separated from those recognized by the OMPI application.
