security/libressl: Fix memory leak and buffer overflow DoS vulnerability

• Update to 2.2.4 (fixing vulnerabilities)
• Create vuxml entry

Differential revision: https://reviews.freebsd.org/D3916
Submitted by: Bernard Spil <brnrd@freebsd.org>
Reviewed by: delphij (secteam)
Approved by: delphij
MFC after: 2015Q4
Security: CVE-2015-5333, CVE-2015-533