Support different framebuffer offsets (fixes #59)

Ryujinx.Core/OsHle/Services/Nv/NvMapFb.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Generic;
+
+namespace Ryujinx.Core.OsHle.IpcServices.NvServices
+{
+    class NvMapFb
+    {
+        private List<long> BufferOffs;
+
+        public NvMapFb()
+        {
+            BufferOffs = new List<long>();
+        }
+
+        public void AddBufferOffset(long Offset)
+        {
+            BufferOffs.Add(Offset);
+        }
+
+        public bool HasBufferOffset(int Index)
+        {
+            if ((uint)Index >= BufferOffs.Count)
+            {
+                return false;
+            }
+
+            return true;
+        }
+
+        public long GetBufferOffset(int Index)
+        {
+            if ((uint)Index >= BufferOffs.Count)
+            {
+                throw new ArgumentOutOfRangeException(nameof(Index));
+            }
+
+            return BufferOffs[Index];
+        }
+    }
+}