Fix beginning-of-defun not jumping to BOF

In batch mode or when font-lock and some other niceties are switched
off, function `syntax-ppss' can modify match data held by function
`beginning-of-defun-raw'.  In that case, `beginning-of-defun' can jump
to some seemingly arbitrary position, and not the actual BOF.

* lisp/emacs-lisp/lisp.el (beginning-of-defun-raw): Save match data
around a call to `syntax-ppss'. (Bug#66218)

lisp/emacs-lisp/lisp.el

@@ -422,7 +422,8 @@ of a defun, nil if it failed to find one."
 				       "\\(?:" defun-prompt-regexp "\\)\\s(")
 			     "^\\s(")
 			                      nil 'move arg))
-                    (nth 8 (syntax-ppss))))
+                    (save-match-data
+                      (nth 8 (syntax-ppss)))))
            found)
 	 (progn (goto-char (1- (match-end 0)))
                 t)))