Refactor SVC handler (#540)

* Refactor SVC handler

* Get rid of KernelErr

* Split kernel code files into multiple folders

Ryujinx.HLE/HOS/Kernel/Memory/KSlabHeap.cs

@@ -0,0 +1,50 @@
+using System.Collections.Generic;
+
+namespace Ryujinx.HLE.HOS.Kernel.Memory
+{
+    class KSlabHeap
+    {
+        private LinkedList<ulong> _items;
+
+        public KSlabHeap(ulong pa, ulong itemSize, ulong size)
+        {
+            _items = new LinkedList<ulong>();
+
+            int itemsCount = (int)(size / itemSize);
+
+            for (int index = 0; index < itemsCount; index++)
+            {
+                _items.AddLast(pa);
+
+                pa += itemSize;
+            }
+        }
+
+        public bool TryGetItem(out ulong pa)
+        {
+            lock (_items)
+            {
+                if (_items.First != null)
+                {
+                    pa = _items.First.Value;
+
+                    _items.RemoveFirst();
+
+                    return true;
+                }
+            }
+
+            pa = 0;
+
+            return false;
+        }
+
+        public void Free(ulong pa)
+        {
+            lock (_items)
+            {
+                _items.AddFirst(pa);
+            }
+        }
+    }
+}