Build: Add Christian Oliff to .mailmap & AUTHORS.txt

Closes gh-4613

Author: mgol

.mailmap

@@ -17,6 +17,8 @@ Carl Fürstenberg <azatoth@gmail.com> <carl@excito.com>
 Charles McNulty <cmcnulty@kznf.com>
 Chris Rebert <github@rebertia.com>
 Chris Rebert <github@rebertia.com> <code@rebertia.com>
+Christian Oliff <christianoliff@pm.me>
+Christian Oliff <christianoliff@pm.me> <christianoliff@yahoo.com>
 Christopher Jones <chris@cjqed.com> cjqed <christopherjonesqed@gmail.com>
 Colin Snover <github.com@zetafleet.com> <colin@alpha.zetafleet.com>
 Corey Frang <gnarf37@gmail.com> <gnarf@gnarf.net>

AUTHORS.txt

@@ -354,3 +354,4 @@ Pat O'Callaghan <patocallaghan@gmail.com>
 JuanMa Ruiz <ruizjuanma@gmail.com>
 Ahmed.S.ElAfifi <ahmed.s.elafifi@gmail.com>
 Sean Robinson <sean.robinson@scottsdalecc.edu>
+Christian Oliff <christianoliff@pm.me>