nemo-file-info.h: Don't use G_DECLARE_INTERFACE - it doesn't allow

us to properly use NemoFile for its vtable - it works but throws a
ton of build warnings and isn't safe.

libnemo-extension/nemo-file-info.h

@@ -31,11 +31,10 @@
 
 G_BEGIN_DECLS
 
-#define NEMO_TYPE_FILE_INFO (nemo_file_info_get_type ())
-
-G_DECLARE_INTERFACE (NemoFileInfo, nemo_file_info,
-                     NEMO, FILE_INFO,
-                     GObject)
+#define NEMO_TYPE_FILE_INFO           (nemo_file_info_get_type ())
+#define NEMO_FILE_INFO(obj)           (G_TYPE_CHECK_INSTANCE_CAST ((obj), NEMO_TYPE_FILE_INFO, NemoFileInfo))
+#define NEMO_IS_FILE_INFO(obj)        (G_TYPE_CHECK_INSTANCE_TYPE ((obj), NEMO_TYPE_FILE_INFO))
+#define NEMO_FILE_INFO_GET_IFACE(obj) (G_TYPE_INSTANCE_GET_INTERFACE ((obj), NEMO_TYPE_FILE_INFO, NemoFileInfoInterface))
 
 #ifndef NEMO_FILE_DEFINED
 #define NEMO_FILE_DEFINED
@@ -44,6 +43,9 @@ G_DECLARE_INTERFACE (NemoFileInfo, nemo_file_info,
 typedef struct NemoFile          NemoFile;
 #endif
 
+typedef NemoFile NemoFileInfo;
+typedef struct _NemoFileInfoInterface NemoFileInfoInterface;
+
 struct _NemoFileInfoInterface 
 {
 	GTypeInterface g_iface;
@@ -82,6 +84,7 @@ struct _NemoFileInfoInterface
 
 GList            *nemo_file_info_list_copy            (GList            *files);
 void              nemo_file_info_list_free            (GList            *files);
+GType             nemo_file_info_get_type             (void);
 
 /* Return true if the file has been deleted */
 gboolean          nemo_file_info_is_gone              (NemoFileInfo *file);