security/xmlsec1: update to v1.3.9

This unbreaks libxml 2.15, where some pointer types went "const",
and the prior FreeBSD ports version of xmlsec1 wanted to error out
instead of seeing warnings (-Werror) and broke.

ChangeLog: https://www.aleksey.com/xmlsec/news.html
required for:
PR: 291316

(This builds with extant libxml2.14 and 2.15, so let's just commit this.)

(cherry picked from commit f09a210a25c877e8f82a8cde9aff64eb5cd958fc)