Gpsd is the GPS daemon on Linux. It implements support for a wide range
of GPS receivers. This patch adds support for gpsd to the Geolocation
module.
The build system can now test for libgps, which provides the public
interface to gpsd's functionality. If found, |GpsdLocationProvider|
is added to the build.
MozReview-Commit-ID: 1kBgFdEZePI
Thomas Zimmermann