Wrap rather than modify most text tools

[dspinellis]

Many tools can be wrapped with a script, rather than modified. This reduces the scope for errors, simplifies porting, allows dgsh to use each system's native tool versions, and improves build speed.

• [ ] paste (coreutils)
• [ ] join (coreutils)
• [ ] sort (coreutils)
• [x] diff (note the GNU --from-file and --to-file options)
• [x] diff3
• [x] cmp (currently not available as a modified binary)
• [x] dgsh-wrap (update so that it can participate in negotiation with flexible IO requirements, with a (arbitrary) as the number of I/O channels)

Still requiring custom implementation:

• coreutils/comm (provides 0-3 outputs)
• coreutils/cut (provids 1-N outputs)
• grep/grep (provides 0-4 outputs)

[dspinellis]

The wrapping needs to take place through a shell script that will collect and examine their arguments. When file arguments are provided, the commands should not accept any input, unless one or more of these file arguments are -.