Enhance ability to support legacy datum transformation definitions

[Norm Olsen]

The RFC 2 implementation included the conversion of all datum transformation definitions (previously maintained in the Datum Dictionary) to the new form of datum transformations as defined by a record in the Geodetic Transformation Dictionary. This appears to work fine for geodetic transformation definitions included in the standard CsMap distribution.

However, it is often the case where end users of applications using the CsMap library have created custom datum definitions (implying a custom geodetic transformation). It would be nice if the CsMap distribution included a/some feature(s) which would support the automatic conversion of such datum definitions to the Geodetic Transformation dictionary format.

[Norm Olsen]

Corrected at revision 1943. The CS_dtcsu function has been modified such that in the case where: 1> a geodetic transformation dictionary does not exist, and 2> the source datum specifies a method of Molodensky, Bursa/Wolf, or Seven Parameter, and 3> the target datum method is marked as "Is WGS84, no conversion required";

The function will generate a cs_GxXform_ object with a an appropriate cs_GeodeticTransform object as a member element, and return such. This fix enables an application which is processing a legacy Datum DIctionary to obtain a definition in the new form for these specific datum transformation types.