MrSID Coordinate System Reading Improvement

[warmerdam]

There are reports that the MrSID driver fails to read coordinate system information in cases where it ought to work. This item is an attempt to collect details on problems so they can be corrected.

Currently GDAL has a few options:

1) uses poImageReader->getWKT() (in openZoomLevel()) to read the wkt string from the mrsid sdk. This is the highest priority way of getting the coordinate system.

2) builds it from the geotiff metadata using GetOGISDefn(), called from MrSIDDataset::Open().

3) fallback on PAM mechanisms if PAM is enabled.

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We need to isolate some problem files demonstrating problems. On review I see:

1) data/tm.sid: Reported WKT has zero for latitude_of_origin and central meridian even though we can see stuff like GEOTIFF_NUM3080ProjNatOriginLongGeoKey=1.000000,-117.474543,33.764462,0.00 0000,0.000000 in the metadata.

[warmerdam]

The client reports that things are working fine for them once they upgraded to a more recent MrSID DSDK.

The problem I identified does not seem to affect folks with modern files.