Bump MODULE_VERSION to 5.1.2

Change-Id: I18d016b62784ec07055e1bede3a9f241306e945a
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Fix for assert in V8 after a string is converted to a symbol

When a string is converted to a symbol by SymbolKey::AsObject, its
symbol_id is undefined.

Change-Id: I63c41d52e309f67a4c8fc2629bdc9fb6a18fd2b5
bug: https://bugreports.qt-project.org/browse/QTBUG-31513
Reviewed-by: Milian Wolff <milian.wolff@kdab.com>
Reviewed-by: Peter Varga <pvarga@inf.u-szeged.hu>
Merge branch 'stable' into dev

Conflicts:
	.qmake.conf
	src/3rdparty/v8/src/objects.cc

Change-Id: I6e3508bd6a8376ac15f354d9002985b79349f684