Fix loading of .user files from Qt Creator 2.4

We do not support loading of files more than 1 minor version old,
but since the current Qt SDK still is based on Creator 2.4 we are
having an exception here.

Fix debugger setup while at it.

Change-Id: I8f974ecd749b46868443de1a6b1e334f33734609
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>