Android: Stop ART from complaining about missing thread names.

The new Android jvm (ART) complains loudly if we attach without
supplying a thread name.

Task-number: QTBUG-35441

Change-Id: I962d613be0db50f3ca9a4c786b36003f31c9db14
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>
Android: Don't accept the volume-key events.

On Android the volume keys are by default connected to the global volume
control and by accepting them we remove this feature. Meaning each
application would need to re-implement this functionality.
Ideally we should only accept the volume keys if they where accepted by
the user to avoid overriding default behavior, but we currently don't
have the infrastructure to do that.

To revert back to the old behavior the env. variable
QT_ANDROID_VOLUME_KEYS can be set.

Task-number: QTBUG-36570

Change-Id: Ib053a40383f2de452f385b19f7795c2fc23fc4fe
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>