add nanovg based osd

nanovg/nvg_shader/D3D11VertexShader.hlsl

@@ -0,0 +1,25 @@
+
+cbuffer VS_CONSTANTS
+{
+    float4x4 dummy;
+    float2 viewSize;
+
+};
+
+struct VS_OUTPUT
+{
+    float4 position   : SV_Position;    // vertex position
+    float2 ftcoord    : TEXCOORD0;      // float 2 tex coord
+    float2 fpos       : TEXCOORD1;      // float 2 position
+};
+
+VS_OUTPUT D3D11VertexShader_Main(float2 pt : POSITION, float2 tex : TEXCOORD0)
+{
+    VS_OUTPUT Output;
+    Output.ftcoord = tex;
+    Output.fpos = pt;
+    Output.position = float4(2.0 * pt.x / viewSize.x - 1.0, 1.0 - 2.0 * pt.y / viewSize.y, 0, 1);
+
+    return Output;
+}
+