NoGui: Return no to yes/no panic alerts.

Also, print to stderr instead of stdio.

Source/Core/Common/MsgHandler.cpp

@@ -99,8 +99,10 @@ bool DefaultMsgHandler(const char* caption, const char* text, bool yes_no, int S
 
 	return IDYES == MessageBox(0, UTF8ToTStr(text).c_str(), UTF8ToTStr(caption).c_str(), STYLE | (yes_no ? MB_YESNO : MB_OK));
 #else
-	printf("%s\n", text);
-	return true;
+	fprintf(stderr, "%s\n", text);
+
+	// Return no to any question (which will in general crash the emulator)
+	return false;
 #endif
 }