Xutf8TextListToTextProperty available when?

[Sebastien]

Is there a special CPP symbol defined when
Xutf8TextListToTextProperty() is available in the X11 distribution? I
am punished with the problem that some OSes have
Xutf8TextListToTextProperty() and others do not so I need a way to
wrap that code in #if defined(xxx) where 'xxx' is a symbol which is
set only if Xutf8* is available in libX11.
Any suggestions very welcome.
-- sebastien