HW/GPFifo: Refactor to class, move to Core::System.

Source/Core/Core/System.h

@@ -43,6 +43,10 @@ namespace Fifo
 {
 class FifoManager;
 }
+namespace GPFifo
+{
+class GPFifoManager;
+}
 namespace Memory
 {
 class MemoryManager;
@@ -111,6 +115,7 @@ public:
   ExpansionInterface::ExpansionInterfaceState& GetExpansionInterfaceState() const;
   Fifo::FifoManager& GetFifo() const;
   GeometryShaderManager& GetGeometryShaderManager() const;
+  GPFifo::GPFifoManager& GetGPFifo() const;
   Memory::MemoryManager& GetMemory() const;
   MemoryInterface::MemoryInterfaceState& GetMemoryInterfaceState() const;
   PixelEngine::PixelEngineManager& GetPixelEngine() const;