QGLContext already uses ownContext to identify when it "owns" QOpenGLContext
and will delete QOpenGLContext when needed. In the other way
QGLContext::fromOpenGLContext creates a QGLContext for QOpenGLContext, and is
now using qGLContextDeleteFunction to identify if QOpenGLContext "owns"
QGLContext by QGLContext only passing a delete function when QOpenGLContext
should delete QGLContext, and by QOpenGLContext calling deleteQGLContext() from
destory() to do the destruction avoiding the previous leak and sometimes crash
on exit.
Change-Id: I65e791776e99b456e4d0c70fc5b5cdb33c975893
Task-number: QTBUG-40286
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>