Optimized memory alignment

Summary:
It's not much, but still 4 bytes saved here by moving the ```bool```s together. (on compilers where ```bool``` is a single byte)
Closes https://github.com/facebook/yoga/pull/319

Reviewed By: gkassabli, passy

Differential Revision: D4383686

Pulled By: emilsjolander

fbshipit-source-id: 9a48eccbb69382850c016aa6ee730526704a15f2

yoga/Yoga.c

@@ -94,16 +94,18 @@ typedef struct YGNode {
   YGStyle style;
   YGLayout layout;
   uint32_t lineIndex;
-  bool hasNewLayout;
+
   YGNodeRef parent;
   YGNodeListRef children;
-  bool isDirty;
 
   struct YGNode *nextChild;
 
   YGMeasureFunc measure;
   YGPrintFunc print;
   void *context;
+
+  bool isDirty;
+  bool hasNewLayout;
 } YGNode;
 
 #define YG_UNDEFINED_VALUES \