Treat an empty MOCP_OPTS as unset.

Amends: r2736

git-svn-id: svn://daper.net/moc/trunk@2737 910807d9-36e0-0310-a014-e9ea483e2ba4
Resequence functions ahead of further work.

git-svn-id: svn://daper.net/moc/trunk@2738 910807d9-36e0-0310-a014-e9ea483e2ba4
Give argc and argv file scope.

git-svn-id: svn://daper.net/moc/trunk@2739 910807d9-36e0-0310-a014-e9ea483e2ba4
Add --echo-args option to show how POPT processed the command line.

git-svn-id: svn://daper.net/moc/trunk@2740 910807d9-36e0-0310-a014-e9ea483e2ba4
Record POPT's command line interpetation in the log for debugging.

git-svn-id: svn://daper.net/moc/trunk@2741 910807d9-36e0-0310-a014-e9ea483e2ba4
Reword error messages to be more user-friendly.

Amends: r2736

git-svn-id: svn://daper.net/moc/trunk@2742 910807d9-36e0-0310-a014-e9ea483e2ba4