Add proper include file for memset.

desmume/src/gfx3d.cpp

@@ -28,6 +28,7 @@
 #include <algorithm>
 #include <assert.h>
 #include <math.h>
+#include <string.h>
 #include "armcpu.h"
 #include "debug.h"
 #include "gfx3d.h"
@@ -2364,4 +2365,4 @@ bool gfx3d_loadstate(std::istream* is, int size)
 	gfx3d.vertlist->count=0;
 
 	return true;
-}
+}