NVDEC implementation using FFmpeg (#443)

* Initial nvdec implementation using FFmpeg

* Fix swapped channels on the video decoder and the G8R8 texture format

* Fix texture samplers not being set properly (regression)

* Rebased

* Remove unused code introduced on the rebase

* Add support for RGBA8 output format on the video image composer

* Correct spacing

* Some fixes for rebase and other tweaks

* Allow size mismatch on frame copy

* Get rid of GetHostAddress calls on VDec

Ryujinx.Graphics/Graphics3d/Texture/LinearSwizzle.cs

@@ -0,0 +1,19 @@
+namespace Ryujinx.Graphics.Texture
+{
+    class LinearSwizzle : ISwizzle
+    {
+        private int Pitch;
+        private int Bpp;
+
+        public LinearSwizzle(int Pitch, int Bpp)
+        {
+            this.Pitch = Pitch;
+            this.Bpp   = Bpp;
+        }
+
+        public int GetSwizzleOffset(int X, int Y)
+        {
+            return X * Bpp + Y * Pitch;
+        }
+    }
+}