ui: also swap sys.stdout with self.fout in _readline
In
17ffb30d9174, _readline was changed to output a space using
raw_input and this was done using sys.stdout directly, not self.fout.
This change broke the command server for JavaHg since it (and other
clients) would see a spurious ' ' on stdout and interpret this as an
unknown channel.
$ hg init t
$ cd t
$ echo a > a
$ hg add a
$ hg commit -m test
$ rm .hg/requires
$ hg tip
abort: index 00changelog.i unknown format 2!
[255]
$ echo indoor-pool > .hg/requires
$ hg tip
abort: unknown repository format: requires features 'indoor-pool' (upgrade Mercurial)!
[255]
$ echo outdoor-pool >> .hg/requires
$ hg tip
abort: unknown repository format: requires features 'indoor-pool', 'outdoor-pool' (upgrade Mercurial)!
[255]