Log Message:
Update msmtp to 1.4.17.
Based on PR 40278 by Leonardo Taccari.

Version 1.4.17:
- Remove most W32-specific code from net.c and use the appropriate gnulib
  modules instead.
- Gnulib upate to 2008-12-24.
- Unified handling of the Gnome and MacOS keyrings. Both are disabled by default
  and must be enabled using --with-*-keyring options.
- Support for SYSCONFDIR/netrc (as a fallback for ~/.netrc) was added by Jim
  Pryor. Thanks!
- Support for the GNOME Keyring was added by Satoru SATOH. Thanks a lot!
- Added a vim syntax file for msmtprc files to scripts/vim. The file was
  written by Simon Ruderich. Thanks!
- Updated the msmtpq/msmtpQ scripts.