Move Windows-specific projects into separate solution.

src/Triangle.Rendering.GDI/Native/GradientTriangle.cs

@@ -0,0 +1,32 @@
+
+namespace TriangleNet.Rendering.GDI.Native
+{
+    using System.Runtime.InteropServices;
+
+    /// <summary>
+    /// The GRADIENT_TRIANGLE structure specifies the index of three
+    /// vertices in the pVertex array in the GradientFill function.
+    /// These three vertices form one triangle
+    /// </summary>
+    /// <remarks>
+    /// http://msdn.microsoft.com/en-us/library/windows/desktop/dd144959.aspx
+    /// </remarks>
+    [StructLayout(LayoutKind.Sequential)]
+    internal struct GradientTriangle
+    {
+        /// <summary>
+        /// The first point of the triangle where sides intersect.
+        /// </summary>
+        public uint Vertex1;
+
+        /// <summary>
+        /// The second point of the triangle where sides intersect.
+        /// </summary>
+        public uint Vertex2;
+
+        /// <summary>
+        /// The third point of the triangle where sides intersect.
+        /// </summary>
+        public uint Vertex3;
+    }
+}