.mailmap: Add entry for Dave McAllister

You can always see the original names/addresses used by passing --no-mailmap to the various git commands. See gitmailmap(5) Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

Author: ac000

.mailmap

@@ -9,6 +9,7 @@ Artem Konev <artem.konev@nginx.com> <41629299+artemkonev@users.noreply.github.co
 Ava Hahn <a.hahn@f5.com> <110854134+avahahn@users.noreply.github.com>
 Dan Callahan <d.callahan@f5.com> <dan.callahan@gmail.com>
 Danielle De Leo <d.deleo@f5.com> <danielle@fastmail.net>
+Dave McAllister <d.mcallister@f5.com> <davemc@gmail.com>
 Dylan Arbour <d.arbour@f5.com> <arbourd@users.noreply.github.com>
 Dylan Arbour <d.arbour@f5.com> <7211830+arbourd@users.noreply.github.com>
 Igor Ippolitov <i.ippolitov@f5.com> <iippolitov@gmail.com>