2012-05-02  cgf-000001

This fix was due to a bug report on the Cygwin mailing list:
http://cygwin.com/ml/cygwin/2012-05/msg00009.html

strace showed that ssh-agent was checking the parent pid and getting a 1
when it shouldn't have.  Other stuff looked ok so I chose to consider
this a smoking gun.

Going back to the version that the OP said did not have the problem, I
worked forward until I found where the problem first occurred -
somewhere around 2012-03-19.  And, indeed, the getppid call returned the
correct value in the working version.  That means that this stopped
working when I redid the way the process pipe was inherited around
this time period.

It isn't clear why (and I suspect I may have to debug this further at
some poit) this hasn't always been a problem but I made the obvious fix.
We shouldn't have been setting ppid = 1 when we're about to pass off to
an execed process.

As I was writing this, I realized that it was necessary to add some
additional checks.  Just checking for "have_execed" isn't enough.  If
we've execed a non-cygwin process then it won't know how to deal with
any inherited children.  So, always set ppid = 1 if we've execed a
non-cygwin process.