Eo: Make sure semi-colons and other directives aren't used in eo_add.

This was already enforced in the legacy version but was not enforced in
the GCC extension version. This change makes sure it's disallowed in
both.

src/lib/eo/Eo.h

@@ -627,7 +627,7 @@ EAPI Eo *_eo_self_get(void);
 # define _eo_add_common(klass, parent, is_ref, ...) \
    ({ \
      Eo * const __eo_self = _eo_add_internal_start(__FILE__, __LINE__, klass, parent, is_ref, EINA_FALSE); \
-     __VA_ARGS__; \
+     (void) (0, ##__VA_ARGS__); \
      (Eo *) _eo_add_end(eo_self, EINA_FALSE); \
     })