Another crash-on-exit bug fixed

[Kevin Funk]

Hey,

I just fixed a kdelibs bug that caused KDevelop to crash on exit in case a 
KCompositeJob was running that had subjobs with parents.

Easy to reproduce:
* Load kdevelop,kdevplatform as project
* Trigger build
* Immediately close KDevelop

-> Crash in ~KCompositeJobPrivate

Scenario:
* Triggering build creates a BuilderJob instance
  with two MakeJobs objects as subjobs
* Note: MakeJobs are children of MakeBuilder
* Both the BuilderJob object and MakeJob A are registered in the runcontroller
* On exit, MakeJob A is killed by the runcontroller
* BuilderJob object is notified about that and removes this subjob
* MakeJob B is still alive
* Eventually the MakeBuilder plugin is unloaded,
  ~MakeBuilder() will delete all MakeJobs ever created.
* Returns to event loop, BuilderJob is auto-deleted
* BuilderJob thinks MakeJob B is still valid and tries to delete it
=> Double-free, crash

The fix in kdelibs is simple: 
KCompositeJob assumes it has ownership over the subjobs but it doesn't 
reparent them in addSubjob(...) -- this is now fixed in 4.11.

For us, this means ~MakeBuilder() no longer deletes MakeJob objects. Fixes the 
above scenario.

To fix in KDevPlatform master I'd need to patch BuilderJob::addSubjob() with 
about 3 lines of code, if you think that's worth it, I can provide a patch.

[1] https://bugs.kde.org/show_bug.cgi?id=230692

-- 
Kevin Funk