OGC WKT strings with AUTHORITY tag must use string codes, not integers

[martin.daly@…]

The EBNF for the AUTHORITY element, from OGC project document 01-009, is as 
follows:

<authority> = AUTHORITY["<name>", "<code>"]

From the revision history in the same document:

1.3 Revision History
1.3.1 00-007r4

...

The significant changes to the specification are as follows:
...
·  The CS_Info.code, and CT_CoordinateTransformation.code, attributes have been 
renamed authorityCode, and converted from a Long Integer to a String.

[warmerdam]

This has been corrected.  The OGR_SRSNode.exportToWkt() method now inspects
the parent node and quotes the value if the parent is AUTHORITY.