fixed processTranscript hang problem

The pipe's FDs got inherited by ssh and it did something that kept them
open even once it exited. Probably involving passing them on to the ssh
mux daemon.

Set close on exec, and all is well.

Kept Annex.Ssh not using processTranscript even though it no longer
hangs when it does use it, just because processTranscript is overkill
there.

This commit was supported by the NSF-funded DataLad project.

Utility/Process/Transcript.hs

@@ -42,6 +42,8 @@ processTranscript'' cp input = do
 {- This implementation interleves stdout and stderr in exactly the order
  - the process writes them. -}
 	(readf, writef) <- System.Posix.IO.createPipe
+	System.Posix.IO.setFdOption readf System.Posix.IO.CloseOnExec True
+	System.Posix.IO.setFdOption writef System.Posix.IO.CloseOnExec True
 	readh <- System.Posix.IO.fdToHandle readf
 	writeh <- System.Posix.IO.fdToHandle writef
 	p@(_, _, _, pid) <- createProcess $ cp