Update checker. (#251)

* Update checker.

* Fix build and enum class.

* Get rid of submodule for httplib.

* Get rid of submodule for curl.

* Minor style changes and fix video.cpp Linux build error.

* CTitleStateIntro_patches: implemented update message

* Update update_checker.cpp

* CTitleStateIntro_patches: fix fade out accepting input

---------

Co-authored-by: Hyper <34012267+hyperbx@users.noreply.github.com>

UnleashedRecomp/install/update_checker.h

@@ -0,0 +1,18 @@
+#pragma once
+
+struct UpdateChecker
+{
+    enum class Result
+    {
+        NotStarted,
+        InProgress,
+        AlreadyUpToDate,
+        UpdateAvailable,
+        Failed
+    };
+
+    static void initialize();
+    static bool start();
+    static Result check();
+    static void visitWebsite();
+};