Clean up compilation log from deprecations

Bunch of misc commits that remove warnings about
deprecation in places where it doesn't affect code much.

https://invent.kde.org/kde/krita/merge_requests/150

Squashed commit of the following:

commit 104297616468769dbbf3efaf8f5bfe639eb1c2ab
Author: Krzysztof Kurek <krzysio.kurek@wp.pl>
Date: Mon Sep 23 13:48:36 2019 +0000

Remove a Qt5.13 function call

commit 232ac69942a6f737dee0f1a984c40b2297e10a30
Author: Krzysztof Kurek <krzysio.kurek@pm.me>
Date: Sat Sep 21 17:14:36 2019 +0200

Remove a CXX specific flag from other targets

commit 6b71a3cc9b734ca52ca5ff54af8248932cfd1144
Author: Krzysztof Kurek <krzysio.kurek@pm.me>
Date: Sat Sep 21 17:12:34 2019 +0200

Even more deprecation removal work

commit 9c4972ad9b65c87fde0125784adf1f616ff967c7
Author: Krzysztof Kurek <krzysio.kurek@pm.me>
Date: Sat Sep 21 14:10:44 2019 +0200

Revert some const-ref changes

Also explicitly mark KisOptionInfo's copy-ctor as being present

commit f13ff926eb5f694a32154bd87159be9600e0df92
Author: Krzysztof Kurek <krzysio.kurek@pm.me>
Date: Fri Sep 20 01:15:47 2019 +0200

A bunch more deprecation fixes

Hopefully it all works... I don't have a second screen to test it thorough.

commit 95c1ee1206f5fb7922833dacd848d97f57729d54
Author: Krzysztof Kurek <krzysio.kurek@pm.me>
Date: Thu Sep 19 20:32:47 2019 +0200

Get rid of a few implicit deprecation warnings

Deleted some superfluous constructor definitions,
explicitly declared operator= of SvgGraphicsContext as default but only for private usage.

commit 35d2f53086332a14406074df539e4fff3958e92e
Author: Krzysztof Kurek <krzysio.kurek@pm.me>
Date: Thu Sep 19 20:30:35 2019 +0200

Simplify KisSwatch class

Removes a warning about implicit deprecation