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/cpp_api/s_item.cpp

@@ -0,0 +1,164 @@
+/*
+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.
+*/
+
+#include "cpp_api/s_item.h"
+#include "common/c_converter.h"
+#include "common/c_content.h"
+#include "lua_api/l_item.h"
+#include "server.h"
+
+bool ScriptApiItem::item_OnDrop(ItemStack &item,
+		ServerActiveObject *dropper, v3f pos)
+{
+	SCRIPTAPI_PRECHECKHEADER
+
+	// Push callback function on stack
+	if(!getItemCallback(item.name.c_str(), "on_drop"))
+		return false;
+
+	// Call function
+	LuaItemStack::create(L, item);
+	objectrefGetOrCreate(dropper);
+	pushFloatPos(L, pos);
+	if(lua_pcall(L, 3, 1, 0))
+		scriptError("error: %s", lua_tostring(L, -1));
+	if(!lua_isnil(L, -1))
+		item = read_item(L,-1, getServer());
+	return true;
+}
+
+bool ScriptApiItem::item_OnPlace(ItemStack &item,
+		ServerActiveObject *placer, const PointedThing &pointed)
+{
+	SCRIPTAPI_PRECHECKHEADER
+
+	// Push callback function on stack
+	if(!getItemCallback(item.name.c_str(), "on_place"))
+		return false;
+
+	// Call function
+	LuaItemStack::create(L, item);
+	objectrefGetOrCreate(placer);
+	pushPointedThing(pointed);
+	if(lua_pcall(L, 3, 1, 0))
+		scriptError("error: %s", lua_tostring(L, -1));
+	if(!lua_isnil(L, -1))
+		item = read_item(L,-1, getServer());
+	return true;
+}
+
+bool ScriptApiItem::item_OnUse(ItemStack &item,
+		ServerActiveObject *user, const PointedThing &pointed)
+{
+	SCRIPTAPI_PRECHECKHEADER
+
+	// Push callback function on stack
+	if(!getItemCallback(item.name.c_str(), "on_use"))
+		return false;
+
+	// Call function
+	LuaItemStack::create(L, item);
+	objectrefGetOrCreate(user);
+	pushPointedThing(pointed);
+	if(lua_pcall(L, 3, 1, 0))
+		scriptError("error: %s", lua_tostring(L, -1));
+	if(!lua_isnil(L, -1))
+		item = read_item(L,-1, getServer());
+	return true;
+}
+
+// Retrieves minetest.registered_items[name][callbackname]
+// If that is nil or on error, return false and stack is unchanged
+// If that is a function, returns true and pushes the
+// function onto the stack
+// If minetest.registered_items[name] doesn't exist, minetest.nodedef_default
+// is tried instead so unknown items can still be manipulated to some degree
+bool ScriptApiItem::getItemCallback(const char *name, const char *callbackname)
+{
+	lua_State* L = getStack();
+
+	lua_getglobal(L, "minetest");
+	lua_getfield(L, -1, "registered_items");
+	lua_remove(L, -2);
+	luaL_checktype(L, -1, LUA_TTABLE);
+	lua_getfield(L, -1, name);
+	lua_remove(L, -2);
+	// Should be a table
+	if(lua_type(L, -1) != LUA_TTABLE)
+	{
+		// Report error and clean up
+		errorstream<<"Item \""<<name<<"\" not defined"<<std::endl;
+		lua_pop(L, 1);
+
+		// Try minetest.nodedef_default instead
+		lua_getglobal(L, "minetest");
+		lua_getfield(L, -1, "nodedef_default");
+		lua_remove(L, -2);
+		luaL_checktype(L, -1, LUA_TTABLE);
+	}
+	lua_getfield(L, -1, callbackname);
+	lua_remove(L, -2);
+	// Should be a function or nil
+	if(lua_type(L, -1) == LUA_TFUNCTION)
+	{
+		return true;
+	}
+	else if(lua_isnil(L, -1))
+	{
+		lua_pop(L, 1);
+		return false;
+	}
+	else
+	{
+		errorstream<<"Item \""<<name<<"\" callback \""
+			<<callbackname<<" is not a function"<<std::endl;
+		lua_pop(L, 1);
+		return false;
+	}
+}
+
+void ScriptApiItem::pushPointedThing(const PointedThing& pointed)
+{
+	lua_State* L = getStack();
+
+	lua_newtable(L);
+	if(pointed.type == POINTEDTHING_NODE)
+	{
+		lua_pushstring(L, "node");
+		lua_setfield(L, -2, "type");
+		push_v3s16(L, pointed.node_undersurface);
+		lua_setfield(L, -2, "under");
+		push_v3s16(L, pointed.node_abovesurface);
+		lua_setfield(L, -2, "above");
+	}
+	else if(pointed.type == POINTEDTHING_OBJECT)
+	{
+		lua_pushstring(L, "object");
+		lua_setfield(L, -2, "type");
+		objectrefGet(pointed.object_id);
+		lua_setfield(L, -2, "ref");
+	}
+	else
+	{
+		lua_pushstring(L, "nothing");
+		lua_setfield(L, -2, "type");
+	}
+}
+
+