dovecot: Improve packaging and include configs

- Add dovenull user, otherwise, dovecot doesn't start
- Build docs to have configuration files for dovecot
- Remove init script as conffile
- Move build options from Makefile to Config.in
- Install section to be more readable
- Refresh patches

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>
(cherry-picked from commit e27438f140)

mail/dovecot/Config.in

@@ -0,0 +1,40 @@
+menu "Select dovecot build options"
+		depends on PACKAGE_dovecot
+
+config DOVECOT_GSSAPI
+	bool "GSSAPI support"
+	default n
+	help
+		Implements GSSAPI support in dovecot.
+
+config DOVECOT_LDAP
+	bool "LDAP support"
+	default n
+	help
+		Implements LDAP support in dovecot.
+
+config DOVECOT_MYSQL
+	bool "MYSQL support"
+	default n
+	help
+		Implements MYSQL support in dovecot.
+
+config DOVECOT_PGSQL
+	bool "PostgreSQL support"
+	default n
+	help
+		Implements PostgreSQL support in dovecot.
+
+config DOVECOT_SQLITE
+	bool "SQLite support"
+	default n
+	help
+		Implements SQLite DB support in dovecot.
+
+config DOVECOT_ICU
+bool "Enable i18n features"
+	default n
+	help
+		Enable ICU (International Components for Unicode) support.
+
+endmenu