mail/fetchmail: mail/fetchmailconf: update to 6.4.2, make Python 3 compatible

Fetchmail updated to new revision 6.4.2

• one bugfix
• manual page updates
• update of Chinese (simplified) translation
• massive fetchmailconf overhaul + Python 3 compatible (requires py-future) + Supports IPv6 and SSL probing
• remove two patches for fetchmail that are in the upstream release
• add a smoke test to fetchmailconf's post-install, and a patch to support that running without X11 $DISPLAY.

PR: 244130
Submitted by: mandree@
Reviewed by: Corey Halpin <chalpin@cs.wisc.edu> (maintainer)
Approved by: Corey Halpin <chalpin@cs.wisc.edu> (maintainer)
MFH: 2020Q1 (bugfixes and fetchmailconf update and Python3 compat.)