Move scriptapi to separate folder (by sapier)

On the lua side, notably minetest.env:<function>(<args>) should now
be replaced by minetest.<function>(<args>).
The old way is and will stay supported for a long time.

Also:
Update and clean up lua_api.txt (by celeron55)
Move EnvRef to lua and remove add_rat and add_firefly (by kahrl)
Add separate src/util/CMakeLists.txt, other minor fixes (by kahrl)

src/script/common/c_internal.h

@@ -0,0 +1,60 @@
+/*
+Minetest
+Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+/******************************************************************************/
+/******************************************************************************/
+/* WARNING!!!! do NOT add this header in any include file or any code file    */
+/*             not being a modapi file!!!!!!!!                                */
+/******************************************************************************/
+/******************************************************************************/
+
+#ifndef C_INTERNAL_H_
+#define C_INTERNAL_H_
+
+class Server;
+class ScriptApi;
+#include <iostream>
+
+#include "lua_api/l_base.h"
+
+extern "C" {
+#include "lua.h"
+}
+
+#define luamethod(class, name) {#name, class::l_##name}
+#define STACK_TO_SERVER(L) get_scriptapi(L)->getServer()
+#define API_FCT(name) registerFunction(L,#name,l_##name,top)
+
+#define REGISTER_LUA_REF(cln)                                                  \
+class ModApi_##cln : public ModApiBase {                                       \
+	public:                                                                    \
+		ModApi_##cln() : ModApiBase() {};                                      \
+		bool Initialize(lua_State* L, int top) {                               \
+			cln::Register(L);                                                  \
+			return true;                                                       \
+		};                                                                     \
+};                                                                             \
+ModApi_##cln macro_generated_prototype__##cln;
+
+
+ScriptApi*  get_scriptapi          (lua_State *L);
+std::string script_get_backtrace   (lua_State *L);
+void        script_error           (lua_State *L, const char *fmt, ...);
+
+#endif /* C_INTERNAL_H_ */