Drift: PMIX_EXTERNAL_AUX_EVENT_BASE

https://github.com/openpmix/pmix-tests/blob/08705b12294fc5020f2af951b9bb10b36b6cec8d/check-standard/etc/openpmix_master-pmix-standard_master.txt#L46-L51

```
#---------------------------------------------------------
# Needs Review:
#  OpenPMIx: 70d5a53ae
#  OpenPMIx PR: 
#---------------------------------------------------------
PMIX_EXTERNAL_AUX_EVENT_BASE
```