Add a "reason" argument to sleep_ms().

sleep_ms() should generally be avoided when possible. This can be used to try
to track down unnecessary sleeps by adding some logging.

This commit on its own doesn't actually add any logging.

UI/RemoteISOScreen.cpp

@@ -457,7 +457,7 @@ RemoteISOConnectScreen::~RemoteISOConnectScreen() {
 	int maxWait = 5000;
 	scanCancelled = true;
 	while (GetStatus() == ScanStatus::SCANNING || GetStatus() == ScanStatus::LOADING) {
-		sleep_ms(1);
+		sleep_ms(1, "remote-iso-scan");
 		if (--maxWait < 0) {
 			// If it does ever wake up, it may crash... but better than hanging?
 			scanAborted = true;