CSM: Add a way to get current locale from CSM

doc/client_lua_api.md

@@ -618,6 +618,7 @@ Minetest namespace reference
 ### Utilities
 
 * `minetest.get_current_modname()`: returns the currently loading mod's name, when we are loading a mod
+* `minetest.get_language()`: returns the currently set gettext language.
 * `minetest.get_version()`: returns a table containing components of the
    engine version.  Components:
     * `project`: Name of the project, eg, "Minetest"

src/script/lua_api/l_client.cpp

@@ -188,6 +188,13 @@ int ModApiClient::l_get_node_or_nil(lua_State *L)
 	return 1;
 }
 
+int ModApiClient::l_get_language(lua_State *L)
+{
+	char *locale = setlocale(LC_ALL, "");
+	lua_pushstring(L, locale);
+	return 1;
+}
+
 int ModApiClient::l_get_wielded_item(lua_State *L)
 {
 	Client *client = getClient(L);
@@ -373,4 +380,5 @@ void ModApiClient::Initialize(lua_State *L, int top)
 	API_FCT(take_screenshot);
 	API_FCT(get_privilege_list);
 	API_FCT(get_builtin_path);
+	API_FCT(get_language);
 }

src/script/lua_api/l_client.h

@@ -66,6 +66,8 @@ private:
 	// get_node(pos)
 	static int l_get_node_or_nil(lua_State *L);
 
+	static int l_get_language(lua_State *L);
+
 	// get_wielded_item()
 	static int l_get_wielded_item(lua_State *L);