Swift: add rewrites for legacy math URLs

Project/lang math URLs were deprecated quite a while ago but we're still
getting a considerable amount of hits to them (which right now are not
routed to Swift at all). Expand the regexp to cover those too, but map
them still to the global containers.

Change-Id: I3c454490b9f9dbc8baf8158566f1c65fa848e6f5