Allow Yoga Pod to be built on any platform (#821)

Summary:
Currently the CocoaPod for Yoga explicitly states platform requirements.

Since the Yoga implementation doesn't depend on any platform features, it would be safe to build it on any platform.

That can be configured by omitting the `platform`/`platforms` key:

> The platform on which this Pod is supported. Leaving this blank means the Pod is supported on all platforms.
>
> http://guides.cocoapods.org/syntax/podspec.html#platform

Among others, that would allow to use the pod in macOS projects
Pull Request resolved: https://github.com/facebook/yoga/pull/821

Reviewed By: passy

Differential Revision: D13848153

Pulled By: davidaurelio

fbshipit-source-id: 5a3e81d81ca97b120f2711bafd3c8b9e0c3f8088

Yoga.podspec

@@ -19,7 +19,7 @@ Pod::Spec.new do |spec|
     :git => 'https://github.com/facebook/yoga.git',
     :tag => spec.version.to_s,
   }
-  spec.platforms = { :ios => "8.0", :tvos => "10.0" }
+  spec.platforms = { :ios => "4.3", :osx => "10.7", :tvos => "10.0", :watchos => "2.0" }
   spec.module_name = 'yoga'
   spec.requires_arc = false
   spec.pod_target_xcconfig = {
@@ -34,6 +34,6 @@ Pod::Spec.new do |spec|
       '-fPIC'
   ]
   spec.source_files = 'yoga/**/*.{c,h,cpp}'
-  spec.public_header_files = 'yoga/{Yoga,YGEnums,YGMacros}.h'
+  spec.public_header_files = 'yoga/{Yoga,YGEnums,YGMacros,YGValue}.h'
 
 end