[Core] SeparateTabBar::currentChanged() fixes.

Emit the signal only if the tab has really been changed.
[Util] Bigger font size for DrawOverlayText.
[Util] Pass brush as well to DrawOverlayText.
[Azoth] Don't try sending a contact as URL to another.
[Azoth MC] Don't suggest unifying with IMUCEntry.
[Core] Handle removed toolbars.
[Core] Added hookTabIsRemoving().
[Core] Fixed a stupid logical error.
[TSM] Use hookTabIsRemoving() instead of windowRemoved().
[Util] Don't reuse IDs in IDPool.
[Azoth Xoox] Initial presence handled for QString().
[Azoth Xoox] Fetch versions for variant-less items as well.
Azoth: change tab name after entry renaming