Remove warnings when building without EFL_BETA_API_SUPPORT

Summary:
efl_alive_get should be a method defined in efl_object.eo, protected by
EFL_BETA_API_SUPPORT while that class is still @beta.
Instead, it is defined in Eo.h, so the BETA guard has to be defined manually.
This was causing some unsighly warnings during "make" and "make check"
(implicit declaration of function ‘efl_invalidating_get’)

Test Plan: make && make check do not throw that warning anymore

Reviewers: zmike, cedric

Reviewed By: zmike

Subscribers: #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D7958

src/lib/eo/Eo.h

@@ -2231,6 +2231,7 @@ eina_value_object_get(Eina_Value *v)
    return r;
 }
 
+#ifdef EFL_BETA_API_SUPPORT
 /**
  * @brief Get if the object is in its main lifetime.
  * @param obj the object to check
@@ -2243,6 +2244,7 @@ efl_alive_get(const Eo *obj)
 {
   return efl_finalized_get(obj) && !efl_invalidating_get(obj) && !efl_invalidated_get(obj);
 }
+#endif /* EFL_BETA_API_SUPPORT */
 
 /**
  * @brief Event triggered when a callback was added to the object