BUG #13488: Wrong netmask calculation

The following bug has been logged on the website:

Bug reference: 13488
Logged by: Taras
Email address: stn(at)inbox(dot)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)