Summary:
Change the `dump-source-location` flag to take a mode kind,
which specifies what to dump.
`loc` will dump just source locations, `range` will dump ranges,
and `both` will dump both.
This simplifies location testing.
Reviewed By: tmikov
Differential Revision: D24200710
fbshipit-source-id: 9cca8ebc49a79c1a14ef7b6875c751da0a8234da