Beta-test version of NSMessagePort on windows (mingw32) ready

[Richard Frith-Macdonald]

I've implemented NSMessagePort/NSMessagePortNameServer for mingw32 in the 
base library using windows mailslots as the transport mechanism and using 
the windows registry for the nameserver mechanism.

The idea is to provide support for distributed objects connections between 
windows apps running for a single user on a single machine in the same way 
that NSMessagePort on unix systems provides secure host-local 
communications.

When using NSMessagePort/NSMessagePortNameServer communications between 
applications should be safe from interception/tampering by other 
users/machines, and the gdomap daemon process does not need to run (and is 
not automatically started).

Anyway, there are doubtless bugs in this, so it needs testing.  Anyone who 
would like to try it out should get and build/install the latest base 
library code from CVS on their windows system, then set the GSMailslot user 
default to enable this (a temporary feature ... once this is debugged we can 
get rid of the default and just have the new implementation enabled all the 
time).

'defaults write NSGlobalDomain GSMailslot YES'

I'm very interested in any reproducible problems ... I'd like to have this 
implementation debugged to the point where it can be made standard by the 
end of the month.