Widgets, iOS: don't tell the input panel to hide on focus out

On iOS, autoSIP is handled by the platform plugin. We therefore
avoid letting widgets tell the input panel to hide on focus out
so we can gain better control over this from the plugin.

Note that we could also set QApplicationPrivate::autoSipEnabled
to false and achieve the same. But since autoSIP is logically set
on iOS, it's better to report it as set in case the app asks.

Change-Id: I96c68bc446a1e299fd57afe03a9e273491df08a7
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>
iOS: only skip activating the most simple popup types

The current approach of not activating transient windows with the
popup flag set was found to be too restrictive, as it would
e.g stop transient dialogs from being able to contain editable
controls.

This patch will restrict the number of popup types that we
skip activation for to only contain a few subtypes.

Task-number: QTBUG-41613
Change-Id: I381a5a79fb4f7082da18a6b4e06a7255ff400b1a
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@digia.com>
Reorganize devicediscovery header

As pointed out in 13b939c7f41bceb2061e549923eab242326e9bb5 the approach
qdevicediscovery_p.h takes is just wrong. The defines it relies on will
often be missing when the header is included from random places in qtbase.
This results in different class layouts. It was working only because the
interface of the class is very limited and the public part was matching
regardless of having the macro defined.

This is now corrected by introducing subclasses and a common, non-variated
base class. QDEVICEDISCOVERY_UDEV is removed completely.

Change-Id: I9c83b5b041440a3a6ea3a604eee4a325d4d74439
Reviewed-by: Louai Al-Khanji <louai.al-khanji@theqtcompany.com>
Reviewed-by: Jørgen Lind <jorgen.lind@theqtcompany.com>