reStructuredText should define a TracLinks role

[naked@…]

As WikiRestructuredTextLinks are a reality now, there should also be an interpreted text role for TracLinks. That is, to be able to say:

There is `WikiPage`:trac: and issue `#12`:trac: here.

Instead of the really awkward current way:

There is |WikiPage| and issue |#12| here.

.. |WikiPage| trac:: WikiPage
.. |#12| trac:: #12

A possible option could be even having the trac interpreted text role as a default, so one could even leave out the ":trac:" part from those, but that would be incompatible with pages that expect it to be the default title-reference role.