3.5.16 and 3.4.50

• Frontier Squid
• XRootD 4.11.3-1.2 for 3.4 (already released in 3.5), including a fix for a core dump seen at OU
• HTCondor 8.8.9 and 8.9.7

Other

• We've built the osg-wn-client and relevant packages for EL8!
• XRootD 5 RC and plugins have successfully passed internal tests