Remove enum count macros

Summary:
@public
Removes all `YG...Count` macros for enums and replaces them with `facebook::yoga::enums::count<YG...>()`.
This removes the need to manually maintain enum counts.

Same as D13597449, working around a defect in clang < 3.9

Reviewed By: amir-shalem

Differential Revision: D13634622

fbshipit-source-id: 344dc70e167b0caf746fe396cedd200f54e52219

yoga/YGNode.cpp

@@ -313,7 +313,8 @@ YGValue YGNode::resolveFlexBasisPtr() const {
 }
 
 void YGNode::resolveDimension() {
-  for (uint32_t dim = YGDimensionWidth; dim < YGDimensionCount; dim++) {
+  using namespace yoga;
+  for (int dim = YGDimensionWidth; dim < enums::count<YGDimension>(); dim++) {
     if (!getStyle().maxDimensions[dim].isUndefined() &&
         YGValueEqual(
             getStyle().maxDimensions[dim], style_.minDimensions[dim])) {