Fixup Enum Generator

Summary:
https://github.com/facebook/yoga/pull/1116 adds a new enum. The enum generator is out of date with copyright header, and some codemods, but it also looks like there were manual changes, types added, etc since generation. I fixed up the script to incorporate generating the changes folks made manually, and also added an enum that was previously only added manually to the C ABI.

Changelog:
[General][Fixed] - Fixup Yoga Enum Generator

Reviewed By: yungsters

Differential Revision: D39922252

fbshipit-source-id: b678fa9a43a896873d8c434745bdaf3f16fd991f

yoga/YGMacros.h

@@ -40,6 +40,49 @@
 #define YG_ENUM_END(name) name
 #endif
 
+#ifdef __cplusplus
+namespace facebook {
+namespace yoga {
+namespace enums {
+
+template <typename T>
+constexpr int count(); // can't use `= delete` due to a defect in clang < 3.9
+
+namespace detail {
+template <int... xs>
+constexpr int n() {
+  return sizeof...(xs);
+}
+} // namespace detail
+
+} // namespace enums
+} // namespace yoga
+} // namespace facebook
+#endif
+
+#define YG_ENUM_DECL(NAME, ...)                               \
+  typedef YG_ENUM_BEGIN(NAME){__VA_ARGS__} YG_ENUM_END(NAME); \
+  WIN_EXPORT const char* NAME##ToString(NAME);
+
+#ifdef __cplusplus
+#define YG_ENUM_SEQ_DECL(NAME, ...)  \
+  YG_ENUM_DECL(NAME, __VA_ARGS__)    \
+  YG_EXTERN_C_END                    \
+  namespace facebook {               \
+  namespace yoga {                   \
+  namespace enums {                  \
+  template <>                        \
+  constexpr int count<NAME>() {      \
+    return detail::n<__VA_ARGS__>(); \
+  }                                  \
+  }                                  \
+  }                                  \
+  }                                  \
+  YG_EXTERN_C_BEGIN
+#else
+#define YG_ENUM_SEQ_DECL YG_ENUM_DECL
+#endif
+
 #ifdef __GNUC__
 #define YG_DEPRECATED __attribute__((deprecated))
 #elif defined(_MSC_VER)