mail/dovecot-pigeonhole: upgrade to v0.4.22.

Changelog:

• Fixed filesystem path handling problem: sieve plugin could have assert-crashed with specific path lengths with: "Panic: file realpath.c: line 86 (path_normalize): assertion failed: (npath_pos + 1 < npath + asize)".
• Sieve extprograms plugin: Large output from "execute" command crashed delivery. Fixed buffering issue in code that handles output from the external program.
• editheader extension: Extensively reworked the low-level implementation of adding and removing headers. This solves a few integer arithmetic problems reported by Clang runtime checks, but also improves code structure and reliability in general.
• imapsieve: Fix assert crash occurring when selected messages are expunged concurrently by the time Sieve filter is to be applied.
• imap4flags extension: Fix binary byte-code corruption occurring when the setflag, addflag, or removeflag command's flag-list is a variable.
• enotify extension: mailto method: Fixed parsing of mailto URI with only a header part.
• enotify extension: mailto method: Make sure "From:" header is set to a usable address and not "(null)".
• Fixed writing address headers to outgoing messages. It sometimes erroneously applied another layer of MIME header encoding.