ENH: support command-line specification of MPI threads (#2791)

- MPI_THREAD_MULTIPLE is usually undesirable for performance reasons,
  but in some cases may be necessary if a linked library expects it.
  Provide a '-mpi-threads' option to explicitly request it.

ENH: consolidate some looping logic within argList

applications/utilities/preProcessing/foamUpgradeCyclics/foamUpgradeCyclics.C

@@ -402,7 +402,6 @@ int main(int argc, char *argv[])
 
     timeSelector::addOptions();
 
-    argList::addOptionCompat("dry-run", {"test", 1806});
     argList::addDryRunOption
     (
         "Test only do not change any files"
@@ -425,7 +424,7 @@ int main(int argc, char *argv[])
 
     instantList timeDirs = timeSelector::select0(runTime, args);
 
-    const bool dryrun = args.found("dry-run");
+    const bool dryrun = args.dryRun();
     if (dryrun)
     {
         Info<< "-dry-run option: no changes made" << nl << endl;