configury: new OPAL_SET_MCA_PREFIX/ORTE_SET_MCA_CMD_LINE_ID macros

   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.
Merge branch 'param2'