Improve tests
(2nd attempt and 65be45e8 was reverted in 15ef0cbc)
Cleanup checkcode $C
Verify some error strings
Create test_dummy2.save in tests (and remove from repo)
I found a nice writeup suggesting that printf
has much better portability than echo
https://www.in-ulm.de/~mascheck/various/echo+printf/
https://unix.stackexchange.com/questions/65803/why-is-printf-better-than-echo
I don't have access to the gcc45 machine, so I'm not sure how to test (or verify if I break it after a merge) but printf has been part of coreutils since at least 2005 so I suspect it will work