autoWatch for symlinked folders not working

We want to use Karma in a "continuous testing" setup with `singleRun: false` and `autoWatch: true` (run as Gulp task). The tests run fine initially and on file changes. Unfortunately, this isn't true for symlinked folders. If we change a file in a folder that is symlinked to a subfolder in the Karma basePath, the watcher is not recognizing it.

Environment: Windows 2008 R2, Karma 0.13.21, Gulp 3.9.1

Start by reproducing the issue with Karma 0.13.21 using singleRun: false and autoWatch: true in the reported Gulp setup on Windows, with a symlinked folder under basePath. Change a file in the symlinked folder and verify that the watcher detects it; done means changes there trigger continuous test runs as they do for non-symlinked folders.

Written by the indexing model from the issue text.