mail/fetchmail: update to 6.4.18 (includes mail/fetchmailconf)

fetchmail-6.4.18 (released 2021-03-27, 30011 LoC):

1. REGRESSION FIX:
2. fetchmailconf: fetchmail 6.4.16 added --sslcertfile to the configuration dump, but fetchmailconf support was incomplete in Git 7349f124 and it could not parse sslcertfile, thus the user settings editor came up empty with console errors printed. Fix configuration parser in fetchmailconf.

1. ROBUSTNESS FIXES:
2. fetchmailconf: do not require fetchmail for -V. do not require Tk (Tkinter) for -d option. This is to fail more gracefully on incomplete installs.
3. TLS code: remove OPENSSL_NO_DEPRECATED macros to avoid portability issues with OpenSSL v3 - these are for development purposes, not production.
4. TLS futureproofing: use SSL_use_PrivateKey_file instead of SSL_use_RSAPrivateKey_file, the latter will be deprecated with OpenSSL v3, and the user's key file might be something else than RSA.

1. TRANSLATION UPDATE: This fine person has contributed an updated translation:
2. fi: Lauri Nurmi [Finnish]

PR: 254619
Submitted by: mandree@
Approved by: Corey Halpin (maintainer)