GDAL core directory getting removed

[ashimitz]

I have been having a problem with the core directory being removed
occassionally. It happens when I abort the configure process before it
completes (forgot to set an option). I tracked the problem down to the
trap command in the configure script, which is doing an rm with the -r
option. I'm not sure if the -r is even needed at all, but it's having
an adverse affect with core being in the list of files to remove,
resulting in the entire GDAL core directory being removed. If the -r
is needed, just move the remove of core to a separate statement. I
have attached the patch for you to add the changes to CVS.