Provide character position information to symbol queries
Summary: Depends on D18937. Ref T13047. When available, provide character positions so external indexers can return more accurate results.
Test Plan: Clicked symbols in Safari, Firefox and Chrome, got sensible-looking character positions.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13047
Differential Revision: https://secure.phabricator.com/D18939