Fix a typo in the ClutterParamSpecFixed declaration

The ClutterParamSpecFixed constructor is declared in the header
as taking ClutterFixed values, but the implementation takes
ClutterUnit values instead. This obviously works because fixed
and units are exactly the same type.

This commit fixes the wrong parameters.

clutter/clutter-fixed.c

@@ -347,9 +347,9 @@ GParamSpec *
 clutter_param_spec_fixed (const gchar  *name,
                           const gchar  *nick,
                           const gchar  *blurb,
-                          ClutterUnit  minimum,
+                          ClutterFixed  minimum,
-                          ClutterUnit  maximum,
+                          ClutterFixed  maximum,
-                          ClutterUnit  default_value,
+                          ClutterFixed  default_value,
                           GParamFlags  flags)
 {
   ClutterParamSpecFixed *fspec;