rocket: fix P/Invoke sig for bool

Summary:
Fixes the `bool` marshaling issue as describe on [MSDN](https://blogs.msdn.microsoft.com/jaredpar/2008/10/14/pinvoke-and-bool-or-should-i-say-bool/) so C# will now act properly.
Closes https://github.com/facebook/css-layout/pull/226

Reviewed By: IanChilds

Differential Revision: D3967349

Pulled By: emilsjolander

fbshipit-source-id: f61d3bb39eb1b0b6e749629825234615b425e930

csharp/Facebook.CSSLayout/CSSNode.cs

@@ -54,6 +54,9 @@ namespace Facebook.CSSLayout
                 _isDisposed = true;
                 Native.CSSNodeFree(_cssNode);
                 GCHandle.FromIntPtr(_context).Free();
+                _children = null;
+                _parent = null;
+                _measureFunction = null;
             }
         }
 
@@ -68,11 +71,7 @@ namespace Facebook.CSSLayout
 
         public void Reset()
         {
-            Native.CSSNodeFree(_cssNode);
-            GCHandle.FromIntPtr(_context).Free();
-            _children = null;
-            _parent = null;
-            _measureFunction = null;
+            Dispose(true);
         }
 
         public bool IsDirty