plplot 5.13.0 soname bump

[Orion Poplawski]

I'll be buiding plplot 5.13 and dependencies shortly.  This has a soname 
bump.


-- 
Orion Poplawski
Manager of NWRA Technical Systems          720-772-5637
NWRA, Boulder/CoRA Office             FAX: [phone]
3380 Mitchell Lane                       orion(a)nwra.com
Boulder, CO 80301                 https://www.nwra.com/