Implement WinRT plugin for positioning

[ChangeLog][QtPositioning][QGeoPositionInfoSource] WinRT backend added.

Change-Id: I00e7725a082aa485c3ab5afcaebd20344b48e07d
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Add snippet app to verify plugin implementation

Useful when creating a new backend to verify behavior.

Change-Id: I7a417aabad4d6dbbe494dcd384ca7af57bd78050
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Fix crash on S4 when running Satellite and Position updates concurrently

This was caused due to unsynchronized access of data between two threads.
The Java satellite updates were sent before the receiving Qt thread could
finish its regular startup. As a consequence the received updates could
not be mapped to a receiving C++ class.

This patch synchronizes the startup and setup of the two threads and
ensures that the relvant data setup on the C++ side is done before the
update thread is started.

In addition some minor debug helpers were added for future references.

Task-number: QTBUG-39082
Change-Id: I1f24ddfcef038fa000801ddb6a3ea0959370f0d3
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>
Add changelog for upcoming Qt 5.3.1 release

Change-Id: I0f709d1066763d2c17950da8b092ecf5f28d9556
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Reviewed-by: Sergio Ahumada <sahumada@blackberry.com>
Fix wrong qreal architecture checks

Since Qt 5.2, qreal is double on all architectures by default,
but some vendors (like Jolla) still use qreal = float.

Instead of old (and broken) architecture checks, use runtime
check sizeof(qreal) == sizeof(double).

Remove the compile-time checks between DBL_MIN/DBL_MAX checks,
these are sufficient on their own.

Change-Id: Iae0c6486afaed0f0653fb3338c048c8f22d1e587
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Reviewed-by: Lisandro Damián Nicanor Pérez Meyer <perezmeyer@gmail.com>
Merge remote-tracking branch 'origin/5.3' into dev

Change-Id: I79173a906d9af146e3707f8cacc60892609f590c
Disable headers precompilation

Workaround to make location compile while the actual issue is
investigated.

Task-number: QTBUG-39692
Change-Id: I0320181594b0b87ed037827dc8cf3608ba5c776e
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Merge "Merge remote-tracking branch 'origin/5.3' into dev" into refs/staging/dev