tests/test-gendoc-zh_CN.t

testlib: move the prune alias into a shell script for Windows

Cramming all of this directly into an alias doesn't play nicely on Windows.
Various test-exchange-obsmarkers-case-XX.t were failing with:

    abort: cannot select revision when creating marker

It turned out that inside debugcommands.debugobsolete(), the following differed
from Linux (where they were empty, at least in the case I debugged):

    'rev': ['.`;'],
    'template': "'{node}\\n'"

#require docutils gettext

  $ $TESTDIR/check-gendoc zh_CN
  checking for parse errors