[shotwell] Fix warning about pointer cast

[Jens Georg <jensgeorg src gnome org>]

commit 875b0f8fa30ddb30eb3ba81ff4db7307c9c7603e
Author: Jens Georg <mail jensge org>
Date:   Thu Nov 17 21:43:21 2016 +0100

    Fix warning about pointer cast
    
    Signed-off-by: Jens Georg <mail jensge org>

 src/PixbufCache.vala           |    2 +-
 src/threads/BackgroundJob.vala |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/PixbufCache.vala b/src/PixbufCache.vala
index 5b79868..6ab4426 100644
--- a/src/PixbufCache.vala
+++ b/src/PixbufCache.vala
@@ -14,7 +14,7 @@ public class PixbufCache : Object {
     
     public class PixbufCacheBatch : Gee.TreeMultiMap<BackgroundJob.JobPriority, Photo> {
         public PixbufCacheBatch() {
-            base (BackgroundJob.JobPriority.compare_func);
+            base ((GLib.CompareDataFunc<BackgroundJob.JobPriority>)BackgroundJob.JobPriority.compare_func);
         }
     }
     
diff --git a/src/threads/BackgroundJob.vala b/src/threads/BackgroundJob.vala
index 2188425..5d259e7 100644
--- a/src/threads/BackgroundJob.vala
+++ b/src/threads/BackgroundJob.vala
@@ -75,7 +75,7 @@ public abstract class BackgroundJob {
             return (int) other - (int) this;
         }
         
-        public static int compare_func(void *a, void *b) {
+        public static int compare_func(JobPriority a, JobPriority b) {
             return (int) b - (int) a;
         }
     }