Fix compilation by moving Graphics exports to a new file

src/CxbxKrnl/CxbxKrnl.cpp

@@ -36,9 +36,6 @@
 
 #define _XBOXKRNL_DEFEXTRN_
 
-// Default to High Performance Mode on machines with dual graphics
-extern "C" {
	__declspec(dllexport) int AmdPowerXpressRequestHighPerformance = 1;	// AMD
	__declspec(dllexport) DWORD NvOptimusEnablement = 0x00000001;		// NVIDIA
}
-
 /* prevent name collisions */
 namespace xboxkrnl
 {

src/HighPerformanceGraphicsEnabler.c

@@ -0,0 +1,4 @@
+#include <Windows.h>
+
+// Default to High Performance Mode on machines with dual graphics
+__declspec(dllexport) int AmdPowerXpressRequestHighPerformance = 1;	// AMD
__declspec(dllexport) DWORD NvOptimusEnablement = 0x00000001;		// NVIDIA