never create a console for command line tools launched from gui apps

commit 219b0d217 fixed forwarding of stdio to a console. unfortunately,
it also forced the creation of a console in the first place if there was
none, which is not part of the contract.
instead, give the child process a window (== console) only we we already
have one. this can be done irrespective of our channel mode, which has
the nice side effect that an explicit redirection to a console would now
also work.

Change-Id: Id25cab5da1ac1cc8ce452127ff95bac8d0a0fea8
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@digia.com>
make the pipe setup code less convoluted

Change-Id: Ied870c892cc3dbbf24a3d9416f685e51a74e5c17
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@digia.com>
add QProcess::Forwarded{Output,Error}Channel

Change-Id: Ifc5ed20c38f3228ef25c28681f296d0456b61abe
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
add QProcess::InputChannelMode

this enables forwarding standard input from the parent process.

Change-Id: I7ee72b9842acc96320d4da693b95dd15d9a7b4d4
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>