Core/Game: Add a dynamic script reloader which reloads scripts modules on changes.

* is responsible for registering plain modules.
* requires compilation with the `WITH_DYNAMIC_LINKING` flag.
* requires further support of the ScriptMgr.

(cherry picked from commit bc0f2b6e5a)

src/server/game/Scripting/ScriptReloadMgr.h

@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2008-2016 TrinityCore <http://www.trinitycore.org/>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef SCRIPT_RELOADER_H
+#define SCRIPT_RELOADER_H
+
+#include <memory>
+#include <string>
+#include "Define.h"
+#include <boost/filesystem/path.hpp>
+
+/// Represents a strong reference to a dynamic library which
+/// provides C++ scripts. As long as one reference to the library exists
+/// the library is kept loaded in the server, which makes it possible to lazy
+/// unload several script types on demand (like SpellScripts), and to
+/// provide multiple versions of the same script to the script factories.
+///
+/// Acquire a new reference through using:
+/// `ScriptReloadMgr::AcquireModuleReferenceOfContext`
+class ModuleReference
+{
+public:
+    virtual ~ModuleReference() { }
+
+    /// Returns the git revision hash of the referenced script module
+    virtual char const* GetScriptModuleRevisionHash() const = 0;
+    /// Returns the name of the referenced script module
+    virtual char const* GetScriptModule() const = 0;
+    /// Returns the path to the script module
+    virtual boost::filesystem::path const& GetModulePath() const = 0;
+};
+
+/// Provides the whole physical dynamic library unloading capability.
+/// Loads, Reloads and Unloads dynamic libraries on changes and
+/// informs the ScriptMgr about changes which were made.
+/// The ScriptReloadMgr is also responsible for watching the source directory
+/// and to invoke a build on changes.
+class TC_GAME_API ScriptReloadMgr
+{
+protected:
+    ScriptReloadMgr() { }
+
+public:
+    virtual ~ScriptReloadMgr() { }
+
+    /// Initializes the ScriptReloadMgr
+    virtual void Initialize() { }
+
+    /// Needs to be called periodically to check for updates on script modules.
+    /// Expects to be invoked in a thread safe way which means it's required that
+    /// the current thread is the only one which accesses the world data.
+    virtual void Update() { }
+
+    /// Unloads the ScriptReloadMgr
+    virtual void Unload() { }
+
+    /// Returns an owning reference to the current module of the given context
+    static std::shared_ptr<ModuleReference> AcquireModuleReferenceOfContext(
+        std::string const& context);
+
+    /// Returns the unique ScriptReloadMgr singleton instance
+    static ScriptReloadMgr* instance();
+};
+
+#define sScriptReloadMgr ScriptReloadMgr::instance()
+
+#endif // SCRIPT_RELOADER_H