Kakadu support : dynamic plugin as an option

[bugbuster]

It would be nice to be able to activate Kakadu support as a dynamic plugin. In particular, it would make it possible to update Kakadu library to a newer version without recompiling the whole GDAL library.

To do so, a couple modification are to be done :

• frmts/jpipkak/makefile.vc : add the target and the plugin name
• frmts/jp2kak/makefile.vc : same thing
• frmts/makefile.vc : add Kakadu special case
• nmake.opt : add Kakadu plugin special case

[bugbuster]

Following our discussion with Even (see ​http://osgeo-org.1560.x6.nabble.com/Use-Kakadu-quot-apps-library-quot-4116-td5326857.html), I have updated the proposed patch :

• it only concerns Windows environment (I do not have a linux PC at hand)
• it is a cumulative patch for #4116 and #6940 (I did not manage to make two separate patches)

Does it sound OK to you ?

[Even Rouault]

In 39503:

Windows build for Kakadu: add capability to build as a plugin, and make it possibly to link only against the Kakadu .lib/.dll instead of incorporating some of its .obj (patch by Phillipe Ghesquiere, fixes #6940, refs #4116)

[Even Rouault]

Patch committed with just a change to comment JP2KAK_PLUGIN = YES in the default nmake.opt (as for other drivers plugin is not the default). Thanks