Fix some compilation warnings

Reported by Jacob Faibussowitsch <jacob.fai@gmail.com>

* lisp/net/eww.el (imagep): Declare.

* src/xdisp.c (note_fringe_highlight): Now compiled only if
HAVE_WINDOW_SYSTEM.

lisp/net/eww.el

@@ -1353,6 +1353,7 @@ within text input fields."
   (setq text-property-default-nonsticky '((face . t) (eww-form . t)
                                           (field . t))))
 
+(declare-function imagep "image.c")
 (defvar text-scale-mode)
 (defvar text-scale-mode-amount)
 (defun eww--rescale-images ()

src/xdisp.c

@@ -35733,6 +35733,7 @@ note_mode_line_or_margin_highlight (Lisp_Object window, int x, int y,
   define_frame_cursor1 (f, cursor, pointer);
 }
 
+#ifdef HAVE_WINDOW_SYSTEM
 
 /* Take proper action when mouse has moved to the window WINDOW, with
    window-local x-position X and y-position Y.  This is only used for
@@ -35811,6 +35812,8 @@ note_fringe_highlight (struct frame *f, Lisp_Object window, int x, int y,
     }
 }
 
+#endif	/* HAVE_WINDOW_SYSTEM */
+
 /* EXPORT:
    Take proper action when the mouse has moved to position X, Y on
    frame F with regards to highlighting portions of display that have