fancyopts: fix handling of "--" value in earlygetopt()

fancyopts: use getopt.gnu_getopt() The issue described in the docstring has been fixed since Python 20ab2260dc93, which is in 2.7. https://hg.python.org/cpython/rev/20ab2260dc93 https://bugs.python.org/issue4458 This fixes the handling of '--' value.

dispatch: replace _earlygetopt(strip=True) with new parser The execution order in cmdalias.__init__() is adjusted to set stripped args to self.givenargs, which is no longer updated in place.