Also introduce 'notexists' for verifying that directory entries do not
exist after a test. Now an explicit supported feature instead of using
"funny" perl in postcheck.
Closes#15046
missing CRs and modified %hostip
lib556/test556: use a real HTTP version to make test reuse more convenient
make sure the weekday in Date headers matches the date
test61: replace stray "^M" (5e 4d) at the end of a cookie with a '^M' (0d)
Gets the test working with external proxies like Privoxy again.
Closes#6463