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/VDec/VpxBitStreamWriter.cs

@@ -0,0 +1,38 @@
+using System.IO;
+
+namespace Ryujinx.Graphics.VDec
+{
+    class VpxBitStreamWriter : BitStreamWriter
+    {
+        public VpxBitStreamWriter(Stream BaseStream) : base(BaseStream) { }
+
+        public void WriteU(int Value, int ValueSize)
+        {
+            WriteBits(Value, ValueSize);
+        }
+
+        public void WriteS(int Value, int ValueSize)
+        {
+            bool Sign = Value < 0;
+
+            if (Sign)
+            {
+                Value = -Value;
+            }
+
+            WriteBits((Value << 1) | (Sign ? 1 : 0), ValueSize + 1);
+        }
+
+        public void WriteDeltaQ(int Value)
+        {
+            bool DeltaCoded = Value != 0;
+
+            WriteBit(DeltaCoded);
+
+            if (DeltaCoded)
+            {
+                WriteBits(Value, 4);
+            }
+        }
+    }
+}