Add portable bit field implementation
Add portable bit field implementation

Summary:
@public
Our usage of C++ bit fields has lead to quite some problems with different compiler setups. Problems include sign bits, alignment, etc.

Here we introduce a portable implementation as a variadic template, allowing the user to store a number of booleans and enums (defined with `YG_ENUM_SEQ_DECL`) in an unsigned integer type of their choice.

This will replace all usages of bit fields across the Yoga code base.

Differential Revision: D16647801

fbshipit-source-id: 230ffab500885a3ad662ea8f19e35a5e9357a563

arthuralee/react-native,facebook/react-native,hoangpham95/react-native,pandiaraj44/react-native,javache/react-native,myntra/react-native,janicduplessis/react-native,exponentjs/react-native,facebook/react-native,myntra/react-native,hammerandchisel/react-native,arthuralee/react-native,exponentjs/react-native,javache/react-native,exponent/react-native,myntra/react-native,facebook/react-native,exponentjs/react-native,exponent/react-native,hoangpham95/react-native,myntra/react-native,exponent/react-native,exponentjs/react-native,pandiaraj44/react-native,javache/react-native,pandiaraj44/react-native,pandiaraj44/react-native,janicduplessis/react-native,javache/react-native,arthuralee/react-native,facebook/react-native,pandiaraj44/react-native,hammerandchisel/react-native,janicduplessis/react-native,pandiaraj44/react-native,hammerandchisel/react-native,hoangpham95/react-native,myntra/react-native,exponentjs/react-native,exponent/react-native,janicduplessis/react-native,facebook/react-native,exponentjs/react-native,hammerandchisel/react-native,exponentjs/react-native,hoangpham95/react-native,exponent/react-native,myntra/react-native,myntra/react-native,arthuralee/react-native,pandiaraj44/react-native,hoangpham95/react-native,hammerandchisel/react-native,hoangpham95/react-native,arthuralee/react-native,hammerandchisel/react-native,hammerandchisel/react-native,janicduplessis/react-native,javache/react-native,exponent/react-native,janicduplessis/react-native,exponent/react-native,javache/react-native,facebook/react-native,facebook/react-native,janicduplessis/react-native,facebook/react-native,exponentjs/react-native,javache/react-native,javache/react-native,hoangpham95/react-native,pandiaraj44/react-native,myntra/react-native,hoangpham95/react-native,myntra/react-native,exponent/react-native,janicduplessis/react-native,javache/react-native,hammerandchisel/react-native,facebook/react-native