Improved export-sets in CMake

[Stephen Kelly]

Yury G.  Kudryashov <urkud.urkud <at> gmail.com> writes:
> > 
> > After that I'd post to the cmake list for initial feedback.
> `git bisect` tells me that 'Remove cmTargetExport constructor' (07901863b6) 
> makes test #53 (ExportImport) fail. I fail to understand why.

I looked into this, and the problem is that you do not initialize the
FrameworkGenerator member, and the class has no default ctor to initialize it
either. You need a line like:

      te->FrameworkGenerator = frameworkGenerator;

Please also add a test or extend the existing test. Also, why is the content of
9bbb00ef9214aef75152f4b8c6147294a57b2103 in a separate commit? It would make
sense to add that stuff in the commit that adds the class.

Do you have time to finish this feature?

Thanks,

Steve.