Summary: Currently we markup `rXabcd`, but not `rX` on its own. Mark these up as repository object names.
Test Plan: Typed `rPOEMS`, `rPOEMS1`, `rPOEMS139893189`, etc.
Reviewers: btrahan, dctrwatson
Reviewed By: btrahan
CC: aran, poop
Differential Revision: https://secure.phabricator.com/D7859
