Allow the 'n' option to decrease the number of arenas below the default, to as little as one arena.  Also, limit the number of arenas to avoid a potential invariant violation in base_alloc().
Allow the 'n' option to decrease the number of arenas below the default,
to as little as one arena.  Also, limit the number of arenas to avoid a
potential invariant violation in base_alloc().

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase