Update xmlrpc-c to 1.51.05+
All xmlrpc-c 1.51.xx releases (currently up to 1.51.04 @ 25/09/2019) have a problem of spamming stderr with debug trace messages that should never have made it to stable/super-stable.
See: https://sourceforge.net/p/xmlrpc-c/code/2981/
This is resolved from 1.52.xx, so would be good to update to this, or a newer version.
EDIT: New Super Stable release 1.51.05 (27/10/2019) has this issue backported in now.