Expose calculateLayoutWithSize in YogaKit

Summary:
calculateLayoutWithSize: can be useful when calculating table/collection view sizes before the views are fully laid out by UIKit.
Closes https://github.com/facebook/yoga/pull/558

Differential Revision: D5104863

Pulled By: emilsjolander

fbshipit-source-id: e0e0c6d502f6745be8d84de8c1b6e24cc25a0352

YogaKit/Source/YGLayout.m

@@ -271,8 +271,6 @@ YG_PROPERTY(CGFloat, aspectRatio, AspectRatio)
   return [self calculateLayoutWithSize:constrainedSize];
 }
 
-#pragma mark - Private
-
 - (CGSize)calculateLayoutWithSize:(CGSize)size
 {
   NSAssert([NSThread isMainThread], @"Yoga calculation must be done on main.");
@@ -293,6 +291,8 @@ YG_PROPERTY(CGFloat, aspectRatio, AspectRatio)
   };
 }
 
+#pragma mark - Private
+
 static YGSize YGMeasureView(
   YGNodeRef node,
   float width,