Summary:
This PR is the C# version of 3a82d2b1a8
The above change moved Yoga away from NaN to facilitate usage of the `-ffast-math` compiler flag. However, that commit forgot to update the C# implementation.
Pull Request resolved: https://github.com/facebook/yoga/pull/817
Differential Revision: D10282642
Pulled By: shergin
fbshipit-source-id: 51681ce12344bc421f346ccc30e2950f4f39dbc6