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/TextureSwizzle.cs

@@ -0,0 +1,11 @@
+namespace Ryujinx.Graphics.Texture
+{
+    public enum TextureSwizzle
+    {
+        _1dBuffer           = 0,
+        PitchColorKey       = 1,
+        Pitch               = 2,
+        BlockLinear         = 3,
+        BlockLinearColorKey = 4
+    }
+}