(help-follow-symbol): New function. Essentially identical to the old

(help-follow-symbol): New function.  Essentially identical to the old
`help-follow', but do not let `push-button' do the work when on an xref.
(help-mode-map): Bind `help-follow-symbol' to "C-c C-c".
(help-xref-symbol-regexp): Make no xref for symbol preceded by the
word `program'.  (From Richard M. Stallman.)
(help-follow-mouse, help-follow): Throw error if not on xref.
Delete no longer used args.  (From Richard M. Stallman.)