Fix cast between incompatible function types warnings

warning: cast between incompatible function types from ‘cairo_status_t (*)(void *, const cairo_point_t *)’ {aka ‘enum _cairo_status (*)(void *, const struct _cairo_point *)’} to ‘cairo_status_t (*)(void *, const cairo_point_t *, const cairo_slope_t *)’ {aka ‘enum _cairo_status (*)(void *, const struct _cairo_point *, const struct _cairo_slope *)’} [-Wcast-function-type]

src/cairo-path-fill.c

@@ -69,6 +69,14 @@ _cairo_filler_line_to (void *closure,
     return status;
 }
 
+static cairo_status_t
+_cairo_filler_add_point (void *closure,
+			 const cairo_point_t *point,
+			 const cairo_slope_t *tangent)
+{
+    return _cairo_filler_line_to (closure, point);
+};
+
 static cairo_status_t
 _cairo_filler_close (void *closure)
 {
@@ -113,7 +121,7 @@ _cairo_filler_curve_to (void		*closure,
     }
 
     if (! _cairo_spline_init (&spline,
-			      (cairo_spline_add_point_func_t)_cairo_filler_line_to, filler,
+			      _cairo_filler_add_point, filler,
 			      &filler->current_point, p1, p2, p3))
     {
 	return _cairo_filler_line_to (closure, p3);

src/cairo-path-fixed.c

@@ -1134,6 +1134,14 @@ _cpf_line_to (void *closure,
     return cpf->line_to (cpf->closure, point);
 }
 
+static cairo_status_t
+_cpf_add_point (void *closure,
+		const cairo_point_t *point,
+		const cairo_slope_t *tangent)
+{
+    return _cpf_line_to (closure, point);
+};
+
 static cairo_status_t
 _cpf_curve_to (void		*closure,
 	       const cairo_point_t	*p1,
@@ -1146,8 +1154,8 @@ _cpf_curve_to (void		*closure,
     cairo_point_t *p0 = &cpf->current_point;
 
     if (! _cairo_spline_init (&spline,
-			      (cairo_spline_add_point_func_t)cpf->line_to,
-			      cpf->closure,
+			      _cpf_add_point,
+			      cpf,
 			      p0, p1, p2, p3))
     {
 	return _cpf_line_to (closure, p3);

src/cairo-path-in-fill.c

@@ -183,6 +183,14 @@ _cairo_in_fill_line_to (void *closure,
     return CAIRO_STATUS_SUCCESS;
 }
 
+static cairo_status_t
+_cairo_in_fill_add_point (void *closure,
+                          const cairo_point_t *point,
+                          const cairo_slope_t *tangent)
+{
+    return _cairo_in_fill_line_to (closure, point);
+};
+
 static cairo_status_t
 _cairo_in_fill_curve_to (void *closure,
 			 const cairo_point_t *b,
@@ -217,7 +225,7 @@ _cairo_in_fill_curve_to (void *closure,
 
     /* XXX Investigate direct inspection of the inflections? */
     if (! _cairo_spline_init (&spline,
-			      (cairo_spline_add_point_func_t)_cairo_in_fill_line_to,
+			      _cairo_in_fill_add_point,
 			      in_fill,
 			      &in_fill->current_point, b, c, d))
     {

src/cairo-path-stroke-traps.c

@@ -930,6 +930,14 @@ line_to_dashed (void *closure, const cairo_point_t *point)
     return CAIRO_STATUS_SUCCESS;
 }
 
+static cairo_status_t
+add_point (void *closure,
+	   const cairo_point_t *point,
+	   const cairo_slope_t *tangent)
+{
+    return line_to_dashed (closure, point);
+};
+
 static cairo_status_t
 spline_to (void *closure,
 	   const cairo_point_t *point,
@@ -1042,7 +1050,7 @@ curve_to_dashed (void *closure,
     cairo_spline_add_point_func_t func;
     cairo_status_t status;
 
-    func = (cairo_spline_add_point_func_t)line_to_dashed;
+    func = add_point;
 
     if (stroker->has_bounds &&
 	! _cairo_spline_intersects (&stroker->current_face.point, b, c, d,

src/cairo-path-stroke.c

@@ -995,6 +995,14 @@ _cairo_stroker_line_to (void *closure,
     return CAIRO_STATUS_SUCCESS;
 }
 
+static cairo_status_t
+_cairo_stroker_add_point_line_to (void *closure,
+				  const cairo_point_t *point,
+				  const cairo_slope_t *tangent)
+{
+    return _cairo_stroker_line_to (closure, point);
+};
+
 static cairo_status_t
 _cairo_stroker_spline_to (void *closure,
 			  const cairo_point_t *point,
@@ -1225,6 +1233,14 @@ _cairo_stroker_line_to_dashed (void *closure,
     return CAIRO_STATUS_SUCCESS;
 }
 
+static cairo_status_t
+_cairo_stroker_add_point_line_to_dashed (void *closure,
+					 const cairo_point_t *point,
+					 const cairo_slope_t *tangent)
+{
+    return _cairo_stroker_line_to_dashed (closure, point);
+};
+
 static cairo_status_t
 _cairo_stroker_curve_to (void *closure,
 			 const cairo_point_t *b,
@@ -1241,13 +1257,13 @@ _cairo_stroker_curve_to (void *closure,
     cairo_status_t status = CAIRO_STATUS_SUCCESS;
 
     line_to = stroker->dash.dashed ?
-	(cairo_spline_add_point_func_t) _cairo_stroker_line_to_dashed :
-	(cairo_spline_add_point_func_t) _cairo_stroker_line_to;
+	_cairo_stroker_add_point_line_to_dashed :
+	_cairo_stroker_add_point_line_to;
 
     /* spline_to is only capable of rendering non-degenerate splines. */
     spline_to = stroker->dash.dashed ?
-	(cairo_spline_add_point_func_t) _cairo_stroker_line_to_dashed :
-	(cairo_spline_add_point_func_t) _cairo_stroker_spline_to;
+	_cairo_stroker_add_point_line_to_dashed :
+	_cairo_stroker_spline_to;
 
     if (! _cairo_spline_init (&spline,
 			      spline_to,