Pypelinery

Upgrades to Pypeline, and simplified CMake test configurations.

• Proper IPv6 addresses with the new [IP]: resource next to IP:
• Prefix SIG: to a daemon to declare how to stop it when the rest is done, without explicit passing it as a cmdline argument
• Prefix PYPE:FORK: to recognise other cues than -- with special forms ^ and $ to replace run_par and run_seq helper scripts
• Postfix argument PYPE:POPCAT: combines multiple preceding arguments into one string (yay, Forth is back!)
• Overrule 1st word as commandname with PYPE:NAME: to make output more readable
• Arguments PYPE:ESC: are literally inserted; serves as an escape
• Prefix or argument ENV: can be used to get/set envvars
• Prefix PYPE:EXIT: replaces old format for specifying alternate-good exit values
• Prefix PIDFILE: names a file holding a PID to send SIG:nals to
• Replace argvcp helper program with builtin INFILE: facility; this allows files to mention Pypeline-allocated resources
• Updates to test/CMakeLists.txt to use these changes

Not yet done: Replace wrap_diameter -- because this involves a pattern, not a literal text as in the PYPE:FORK: prefix. If this turns out to be generally useful, we'll add that functionality some day, I'm sure.