printGPSCoords() returned a newly allocated C-style string. Most
callers simply made a QString out of it and freed the C-style string.
This is paradoxical, as printGPSCoords internally works with QStrings
and converts them to C-style on return.
Therefore, let printGPSCoords() return a QString and create a
printGPSCoordsC() wrapper for the two C-callers.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>