ecore: use standard LC_ALL instead of __LC_ALL in systemd module

The former is a POSIX name, the latter is non-standard. I don't
know why the latter was used, considering glibc literally has
just #define LC_ALL __LC_ALL, but change it and unbreak build
on musl and other systems.

src/modules/ecore/system/systemd/ecore_system_systemd.c

@@ -163,7 +163,7 @@ static void _locale_get(void *data EINA_UNUSED, const Eldbus_Message *msg,
 
         setenv(type, value, 1);
      }
-   setlocale(__LC_ALL, "");
+   setlocale(LC_ALL, "");
 
  end:
    ecore_event_add(ECORE_EVENT_LOCALE_CHANGED, NULL, NULL, NULL);