These functions are only declared in the non-installed, private header

file.  Add declarations for now, so that things keep building.

This looks like it fixes a pointer trucation issue.

Submitted upstream: <https://rt.cpan.org/Ticket/Display.html?id=145548>

diff -ur Goo-Canvas-0.06.orig/goocanvas-perl.h Goo-Canvas-0.06/goocanvas-perl.h

--- Goo-Canvas-0.06.orig/goocanvas-perl.h	2007-09-29 02:59:38.000000000 +0200

+++ Goo-Canvas-0.06/goocanvas-perl.h	2022-12-09 21:09:33.927299572 +0100

@@ -9,6 +9,10 @@

 #include "cairo-perl.h"

 #include "goocanvas.h"

+/* From goocanvasprivate.h.  */

+cairo_pattern_t* goo_canvas_cairo_pattern_from_pixbuf (GdkPixbuf *pixbuf);

+cairo_surface_t* goo_canvas_cairo_surface_from_pixbuf (GdkPixbuf *pixbuf);

+

 /* FIXME: How to avoid compile error in autogen.h */

 #define GooCairoPattern cairo_pattern_t

 #define GooCairoMatrix cairo_matrix_t