Generate alphanumerical random strings.
Prior this change curl used to create random hex strings. This was
mostly okay, but having alphanumerical random strings is better: The
strings have more entropy in the same space.
The MIME multipart boundary used to be mere 64-bits of randomness due
to being 16 hex chars. With these changes the boundary is 22
alphanumerical chars, or little over 130 bits of randomness.
Closes#11838
- they are mostly pointless in all major jurisdictions
- many big corporations and projects already don't use them
- saves us from pointless churn
- git keeps history for us
- the year range is kept in COPYING
checksrc is updated to allow non-year using copyright statements
Closes#10205
