Add QBluetoothDeviceInfo::UnknownCoreConfiguration enum value

The value is needed for platforms which do not provide this type
information. An example are Android versions below 18.

The enum was added in Qt 5.4. Therefore we need to add
the missing \since tag too.

Change-Id: I23582e7500d8da6740b281ba9821d028c4f33e05
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Merge remote-tracking branch 'gerrit/5.4' into btle

Change-Id: Id28ba006101e64d2b0acd294ffc84be50993cb9e
Android: Don't add the same device twice to DeviceDiscovery results

In particular this happens when scanning for BTLE devices

Change-Id: Ia75ba6f510e4e47a92992638f5bb919072fceb13
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Merge "Merge remote-tracking branch 'gerrit/5.4' into btle" into refs/staging/btle