Man-highlight-references is a compiled Lisp function in `man.el'.

(Man-highlight-references &optional XREF-MAN-TYPE)

Highlight the references on mouse-over.
References include items in the SEE ALSO section,
header file (#include <foo.h>), and files in FILES.
If optional argument XREF-MAN-TYPE is non-nil, it used as the
button type for items in SEE ALSO section. If it is nil, the
default type, `Man-xref-man-page' is used for the buttons.