tests/test-mq-qsave.t

scmutil: split platform-specific bits into their own modules

This parallels what's done for the util module, which imports either
mercurial.posix or mercurial.windows as 'platform' and then slurps the
appropriate functions into its own namespace.

  $ echo "[extensions]" >> $HGRCPATH
  $ echo "mq=" >> $HGRCPATH

  $ hg init

  $ echo 'base' > base
  $ hg ci -Ambase
  adding base

  $ hg qnew -mmqbase mqbase

  $ hg qsave
  $ hg qrestore 2
  restoring status: hg patches saved state