Windows 10 is reported as Windows 8.1

In MC-84778:

Kumasasa: Are you using Windows 10 (as in the Environment field) or Windows 8.1 (as in the Crash report) ?

Victor: I'm using windows 10, i already noticed the game detects it as Windows 8.1 when launching game, in snooper settings and in crash reports.

-- System Details --
Details:
	Minecraft Version: 15w31c
	Operating System: Windows 8.1 (amd64) version 6.3
	Java Version: 1.8.0_51, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation