ARM64Emitter: Implement instructions to move data to/from SP

Core/MemMap.cpp

@@ -253,6 +253,7 @@ void MemoryMap_Shutdown(u32 flags) {
 
 void Init() {
 	// On some 32 bit platforms, you can only map < 32 megs at a time.
+	// TODO: Wait, wtf? What platforms are those? This seems bad.
 	const static int MAX_MMAP_SIZE = 31 * 1024 * 1024;
 	_dbg_assert_msg_(MEMMAP, g_MemorySize < MAX_MMAP_SIZE * 3, "ACK - too much memory for three mmap views.");
 	for (size_t i = 0; i < ARRAY_SIZE(views); i++) {