tests/test-config-case.t

util: concentrate quoting knowledge to windows.py quotecommand()

This fixes all callers of util.quotecommand() and place special knowledge
of the bugfix in 2.7.1 in a single platform specific place.

  $ echo '[Section]' >> $HGRCPATH
  $ echo 'KeY = Case Sensitive' >> $HGRCPATH
  $ echo 'key = lower case' >> $HGRCPATH

  $ hg showconfig Section
  Section.KeY=Case Sensitive
  Section.key=lower case