Introduce CSSAssertSetFailFunc and CSSAsserFail to throw managed exception

Summary:
- Define CSS_ASSERT_FAIL_ENABLED for P/Invoke (Visual Studio project already has it)
- Pass managed delegate pointer to unmanaged side via P/Invoke.
- CSSAssertFail will call the managed delegate when assert failed.
- The delegate will throw managed exception.

Reviewed By: emilsjolander

Differential Revision: D3982084

fbshipit-source-id: 058a87c10ca89238362be4d8759cc00dd0c9b376

csharp/Facebook.CSSLayout/CSSNode.cs

@@ -93,6 +93,7 @@ namespace Facebook.CSSLayout
                 throw new InvalidOperationException("Allready initialized node");
             }
 
+            CSSAssert.Initialize();
             _cssNode = Native.CSSNodeNew();
             _children = new List<CSSNode>(4);
             Native.CSSNodeSetPrintFunc(_cssNode, _printFunc);