Add hg_root values to hg.m.o. trees
Add hg_root values to hg.m.o. trees

This will allow the mozsearch code to provide customized log/raw links
for files in these repos, rather than just pointing to URLs with
mozilla-central hard-coded in them.

bill-mccloskey/mozsearch-mozilla,bill-mccloskey/mozsearch-mozilla,bill-mccloskey/mozsearch-mozilla