Add changelog for Qt 5.4.0 release

Change-Id: Iebf89c615421ec39c1e5ce73b89d1f7e25372b39
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@theqtcompany.com>
Bump version

Change-Id: Id247df4d821c8041cd14748e0cda909eb55cce25
Merge remote-tracking branch 'origin/5.4' into dev

Conflicts:
	.qmake.conf

Change-Id: I9211d15553ae9b316784183a448bf1fbab1b07fc