Added BitUtils
Added BitUtils

Summary:
Adds BitUtils to be used later instead of Bitfield.h

##Changelog:
[Internal][Yoga] : Adds BitUtils to be used later instead of Bitfield.h

Reviewed By: astreet

Differential Revision: D18519609

fbshipit-source-id: 8353929543505a7d80d66281adb801d34372beed

facebook/litho,facebook/litho,facebook/litho,facebook/litho,facebook/litho,facebook/litho