Went through CURLOPTTYPE_STRINGPOINT and CURLOPTTYPE_SLISTPOINT options
and clarified:
- what happens when setting the option *again*
- setting to NULL disables/restores to default
- libcurl does not copy the slist for options using a such
Closes#14846
- make DEFAULT sections less repetitive
- make historic mentions use HISTORY
- generate the protocols section on `# %PROTOCOLS%` instead of guessing
where to put it
- generate the availability section on `# %AVAILABILITY%` instead of
guessing where to put it
- make the protocols section more verbose
Closes#14227
- generate AVAILABILITY manpage sections automatically - for consistent
wording
- allows us to double-check against other documumentation (symbols-in-versions
etc)
- enables proper automation/scripting based on this data
- lots of them were wrong or missing in the manpages
- several of them repeated (sometimes mismatching) backend support info
Add test 1488 to verify "added-in" version numbers against
symbols-in-versions.
Closes#14217
