Log Message:
Update mail/claws-mail to 3.7.8, and sync plugins.

Upstream changes:

* Bug fixes:
- rfe 2309, 'Shortcuts should not be modifiable by default'
- bug 2313, 'CLI quicksearch sometimes returns the same
messages twice'
- bug 2317, 'Action results in "Bad file descriptor"
- PGP/Core: Win32 build fix
- NNTP: fix replying (broken in corner case)
- fix configure option --disable-manual
- One more GTK+ 2.22 build fix
- Debian bug 599547, 'Please re-introduce quick shortcut for
marking as spam'