Support shared color mask, implement more shader instructions

Support shared color masks (used by Nouveau and maybe the NVIDIA
driver).
Support draw buffers (also required by OpenGL).
Support viewport transform disable (disabled for now as it breaks some
games).
Fix instanced rendering draw being ignored for multi draw.
Fix IADD and IADD3 immediate shader encodings, that was not matching
some ops.
Implement FFMA32I shader instruction.
Implement IMAD shader instruction.

Ryujinx.Graphics.OpenGL/HwCapabilities.cs

@@ -7,10 +7,12 @@ namespace Ryujinx.Graphics.OpenGL
     {
         private static Lazy<bool> _supportsAstcCompression = new Lazy<bool>(() => HasExtension("GL_KHR_texture_compression_astc_ldr"));
 
+        private static Lazy<int> _maximumViewportDimensions    = new Lazy<int>(() => GetLimit(All.MaxViewportDims));
         private static Lazy<int> _storageBufferOffsetAlignment = new Lazy<int>(() => GetLimit(All.ShaderStorageBufferOffsetAlignment));
 
         public static bool SupportsAstcCompression => _supportsAstcCompression.Value;
 
+        public static int MaximumViewportDimensions    => _maximumViewportDimensions.Value;
         public static int StorageBufferOffsetAlignment => _storageBufferOffsetAlignment.Value;
 
         private static bool HasExtension(string name)