version skew between GreenCard and hugs

[Alastair Reid]

> 1.  Why is this source file duplicated? 

For the benefit of those who want to use greencard but don't want
 to use a source distribution of Hugs.

A better solution to this (rather lame) argument would have been
adding GreenCard.h to the binary distributions.

> 2.  Are there any version compatibility issues to worry about here?

Hugs uses version numbers for the API that Greencard uses.
Greencard currently uses version 2 whilst Hugs supports 2 and 3.
There is a dynamic check that the version number is ok.
I believe that the check reflects reality - i.e., that it really
is ok to use greencard and the greencard-supplied API with a modern 
version of Hugs.

> I'm a little perplexed as to why the latest release of hugs
> has a more up-to-date "GreenCard.h" than GreenCard itself.

Because GreenCard.h is really a definition of the FFI-support API
and the FFI support has been updated much more recently than
GreenCard.

Perhaps the name of the file should be changed and copies included 
in binary distributions.

--
Alastair Reid

ps The CVS repository for Hugs is online so you could track down
who is to blame for changes like this.  (Me, in this case.)