Dsh

We currently use two different dsh implementations:

• The perl dsh is installed on zwinger as "dsh". It has a handy interactive mode. It checks to see if servers are up before it tries to log in to them. It sorts the output by server, using a small buffer, and so for tasks like compilation that do a lot of output, the task becomes effectively serialized as the stdout blocks for the other servers while waiting for the first server to complete. Its single quote handling is buggy.
• Dancer's dsh is installed on zwinger as "ddsh". Output is not sorted by server, so it's faster and uglier. Also it's written in C and doesn't do the slow server check before login. It's used by scripts such as sync-file and scap which need speed.