src/guicontrol.cc: Fix assertion failure when double-clicking on the
survey with wx2.9.
src/: Hook up GPX export options to export entrances, fixed points,
and/or exported points, and specify coloured pin symbols for these
types of stations.  These options now default to what's being shown
in the survey view, like other export options.   GPX export
"creator" how includes the Survex version and website URL, and the
survey title is includes as a <name> tag inside the <gpx> tag.
src/printwx.cc: Fix export and (the built-in) print preview to
actually use the options selected in the dialog rather than those
set when the dialog was created.