RTEMS-posix: free the epicsEventOSD in epicsEventDestroy()

epicsEventCreate() mallocs the wrapper but epicsEventDestroy() only
destroys the embedded rtems_binary_semaphore, leaking one heap block
per event lifecycle on every RTEMS >= 5 build.

modules/libcom/src/osi/os/RTEMS-posix/osdEvent.c

@@ -45,6 +45,7 @@ LIBCOM_API void
 epicsEventDestroy(epicsEventId pSem)
 {
     rtems_binary_semaphore_destroy(&pSem->rbs);
+    free(pSem);
 }
 
 LIBCOM_API epicsEventStatus