BUG #13488: Wrong netmask calculation

The following bug has been logged on the website:

Bug reference:      13488
Logged by:          Taras
Email address:      stn@inbox.ru
PostgreSQL version: 9.4.4
Operating system:   CentOS 6.5
Description:

database=# select inet(routedest), inet(routemask) from iprouteinterface
group by routedest, routemask order by routedest limit 3;
   inet    |    inet
-----------+-------------
 0.0.0.0   | 0.0.0.0
 10.1.0.0  | 255.255.0.0
 10.10.0.0 | 255.255.0.0
(3 rows)

database=# select inet(routedest), cidr(routemask) from iprouteinterface
group by routedest, routemask order by routedest limit 3;
   inet    |      cidr
-----------+----------------
 0.0.0.0   | 0.0.0.0/32
 10.1.0.0  | 255.255.0.0/32
 10.10.0.0 | 255.255.0.0/32
(3 rows)
database=# select routedest, network(inet(routemask)) from iprouteinterface
group by routedest, routemask order by routedest limit 3;
 routedest |    network
-----------+----------------
 0.0.0.0   | 0.0.0.0/32
 10.1.0.0  | 255.255.0.0/32
 10.10.0.0 | 255.255.0.0/32
(3 rows)