dovecot: use underscored users _dovecot and _dovenull.

These users should not own any files, so renaming is unproblematic.
Restarting dovecot fixes permissions in /var/run.

srcpkgs/dovecot/patches/system-account.patch

@@ -0,0 +1,15 @@
+--- src/master/master-settings.c.orig
++++ src/master/master-settings.c
+@@ -209,9 +209,9 @@
+ 	.protocols = "imap pop3 lmtp",
+ 	.listen = "*, ::",
+ 	.ssl = "yes:no:required",
+-	.default_internal_user = "dovecot",
+-	.default_internal_group = "dovecot",
+-	.default_login_user = "dovenull",
++	.default_internal_user = "_dovecot",
++	.default_internal_group = "_dovecot",
++	.default_login_user = "_dovenull",
+ 	.default_process_limit = 100,
+ 	.default_client_limit = 1000,
+ 	.default_idle_kill = 60,

srcpkgs/dovecot/template

@@ -2,7 +2,7 @@
 # revbump dovecot-plugin-pigeonhole when updating dovecot!
 pkgname=dovecot
 version=2.3.2.1
-revision=1
+revision=2
 build_style=gnu-configure
 configure_args="--with-moduledir=/usr/lib/dovecot/modules --with-sql=plugin
  --disable-static --with-pam --with-mysql --with-pgsql --with-lucene
@@ -42,7 +42,7 @@ fi
 
 # For SSL support.
 depends="ca-certificates"
-system_accounts="dovecot dovenull"
+system_accounts="_dovecot _dovenull"
 dovecot_homedir="/var/chroot"
 dovenull_homedir="/var/chroot"
 conf_files="/etc/dovecot/*.conf /etc/dovecot/conf.d/*.conf /etc/ssl/dovecot-openssl.cnf"