Log Message:
mail/dovecot2-pigeonhole: update to 0.5.6

Update dovecot2-pigeonhole to 0.5.6.

v0.5.6 2019-04-30  Aki Tuomi <aki.tuomi@open-xchange.com>

	+ sieve: Redirect loop prevention is sometimes ineffective. Improve
	  existing loop detection by also recognizing the
	  X-Sieve-Redirected-From header in incoming messages and dropping
	  redirect actions when it points to the sending account. This header
	  is already added by the redirect action, so this improvement only
	  adds an additional use of this header.
	- sieve: Prevent execution of implicit keep upon temporary failure
	  occurring at runtime.