-void xbt_context_set_jmutex(xbt_context_t context,void *jm){}
-void* xbt_context_get_jmutex(xbt_context_t context){return NULL;}
-void xbt_context_set_jcond(xbt_context_t context,void *jc){}
-void* xbt_context_get_jcond(xbt_context_t context){return NULL;}