[babl] Fix const warning

[Daniel Sabo <daniels src gnome org>]

commit ffaef3a7c10412820a887e343a9452dcce8c9235
Author: Daniel Sabo <DanielSabo gmail com>
Date:   Wed Mar 5 04:56:15 2014 -0800

    Fix const warning

 babl/babl-util.c |    6 +++---
 babl/babl-util.h |    6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)
---
diff --git a/babl/babl-util.c b/babl/babl-util.c
index 92977ac..f68a684 100644
--- a/babl/babl-util.c
+++ b/babl/babl-util.c
@@ -88,9 +88,9 @@ babl_process_cost (long ticks_start,
 }
 
 double
-babl_rel_avg_error (double *imgA,
-                    double *imgB,
-                    long    samples)
+babl_rel_avg_error (const double *imgA,
+                    const double *imgB,
+                    long          samples)
 {
   double error = 0.0;
   long   i;
diff --git a/babl/babl-util.h b/babl/babl-util.h
index bdaeec8..e04120e 100644
--- a/babl/babl-util.h
+++ b/babl/babl-util.h
@@ -27,7 +27,7 @@ babl_process_cost (long ticks_start,
                    long ticks_end);
 
 double
-babl_rel_avg_error (double *imgA,
-                    double *imgB,
-                    long    samples);
+babl_rel_avg_error (const double *imgA,
+                    const double *imgB,
+                    long          samples);
 #endif