MFH: r420399

• Update to 1.7.3 (security fixes)
• Bump library version in pkg-plist

ref: https://lists.gnupg.org/pipermail/gnupg-announce/2016q3/000395.html

Reviewed by: amdmi3 (mentor)
Approved by: amdmi3 (mentor)
Differential Revision: D7558

Approved by: ports-secteam (junovitch)