...finding dubious additions to namespace std (concentrating on functions for
now).  C++17 [namespace.std]/1: "The behavior of a C ++ program is undefined if
it adds declarations or definitions to namespace std or to a namespace within
namespace std unless otherwise specified."

This found

ad4c7b97752b4da73808402604d6f96b39d920f5 "Avoid declaring function templates in
 namespace std"
042e30a3dc057aef4a02d95960e4dd4fb8d083ae "Avoid adding a function template
 declaration to namespace std"
cae9240a76cdb0eeed92421930d3b4cbef0ac201 "Avoid adding a function declaration to
 namespace std"

Change-Id: Ic2ba54e2a8bf931d5c58cedf499c0d1229eb2166
Reviewed-on: https://gerrit.libreoffice.org/78220
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>