Add Create support for Surfer 7 Binary grid format

[bpayne]

Please add create support for the Surfer 7 Binary grid format. This includes the use of the GPSeismic format (identical to the Surfer 7 format). To this end, we have added these capabilities to the gs7bgdataset.cpp file. The modifications to support these capabilities are in the attached file.

We have been using these capabilities in our own product for several years now, but would like to contribute this back to the community and make our build process with taking GDAL upgrade easier.

[bpayne]

Updated version of gdal/frmts/gsg/gs7bgdataset.cpp

[Even Rouault]

Applied. Thanks. Note that I've also done a bit of cleanup (in the GSAG and GSBG drivers too, from which I see the new code was mostly derived). I've removed the GPSEIS driver too : I didn't see the point of having 2 drivers that share exactly the same code...

r24584 /trunk/ (autotest/gdrivers/gsg.py gdal/frmts/gsg/gs7bgdataset.cpp): GS7BG: implement Create() and CreateCopy() (contributed by Russell Jurgensen, #4707)

r24585 /trunk/gdal/frmts/gsg/ (gsagdataset.cpp gsbgdataset.cpp): A bit of cleanup in GSAG and GSBG drivers

[bpayne]

Thanks for your prompt response. In reviewing the changes, I noticed that you also removed the delete capabilities for this format. Does this mean GDAL will revert to using the default delete support or is deletion capability for Surfer files no longer present?

[Even Rouault]

The specialized Delete code was not necessary. There's a generic implementation at the GDALDataset level that does that already.