Ticket 71 - Detect if we have event_set_mem functions
Bug Description: On some platforms libevent is not built with the ability to
override the memory functions. We should detect this.
Fix Description: If libevent does define EVENT_SET_MEM_FUNCTIONS_IMPLEMENTED
we can use this feature.
https://fedorahosted.org/nunc-stans/ticket/71
Author: wibrown
Review by: mreynolds (Thanks!)