MFH: r404275

graphics/librsvg2: update 2.40.10 -> 2.40.12

PR: 205502
Approved by: gnome (kwm)
Approved by: ports-secteam (feld)
Security: CVE-2015-7558
Security: https://vuxml.FreeBSD.org/freebsd/d6c51737-a84b-11e5-8f5c-002590263bf5.html