Revert "lua: Make sure it builds with --disable-nls."

This reverts commit 29847260.
I'd rather have a stable lua api (besides, vlclua_gettext is already a noop).

modules/misc/lua/intf.c

@@ -211,9 +211,7 @@ int Open_LuaIntf( vlc_object_t *p_this )
     luaopen_video( L );
     luaopen_vlm( L );
     luaopen_volume( L );
-#ifdef ENABLE_NLS
     luaopen_gettext( L );
-#endif
 
     /* clean up */
     lua_pop( L, 1 );

modules/misc/lua/libs.h

@@ -42,8 +42,6 @@ void luaopen_variables( lua_State * );
 void luaopen_video( lua_State * );
 void luaopen_vlm( lua_State * );
 void luaopen_volume( lua_State * );
-#ifdef ENABLE_NLS
 void luaopen_gettext( lua_State * );
-#endif
 
 #endif