Fix call-seq return values in C extensions

[zonuexe]

Some call-seq comments in C extensions did not match the actual return values. This fixes them (documentation only, no behavior change).

• openssl: syswrite_nonblock accepts opts and can return a symbol with exception: false
• strscan: match? returns the match size (not a position); skip was missing the -> arrow; scan_full and scan_byte can return values other than documented
• date: Date#new_start had a stray ] in its call-seq
• io/console: getch can return nil on EOF or timeout

[github-actions]

The following files are maintained in the following upstream repositories:

• https://github.com/ruby/date
  • ext/date/date_core.c
• https://github.com/ruby/io-console
  • ext/io/console/console.c
• https://github.com/ruby/openssl
  • ext/openssl/ossl_ssl.c
• https://github.com/ruby/strscan
  • ext/strscan/strscan.c

Please file a pull request to the above instead. Thank you!

[zonuexe]

I submitted separate PRs.

• Fix stray bracket in Date#new_start call-seq date#171
• Document that getch can return nil io-console#130
• Document syswrite_nonblock opts and symbol return openssl#1055
• Fix call-seq return values strscan#207