Emit the last known position when Geoclue positioning is started.

The QML position source already essentially does this as its position
property is set to the last known position on construction.

Change-Id: I3e41886348a218751ab0872e8d78ac92cb72dc0b
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Fix requesting single updates from Geoclue plugin.

Geoclue providers are expected to return a position update straight
away, otherwise the geoclue-master blocks when positioning is started.
This means that a position update with no longitude and latitude values
is not an error.

Change the Geoclue plugin to ignore these position updates, instead
waiting for the specified timeout before aborting.

Change-Id: I80b3c4cfdc31da78660f7435fdfac03963688c5a
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Merge remote-tracking branch 'origin/stable' into dev

Change-Id: I52bbea59f75f74beac90c6368b50558e865304fa