[babl] extensions/gray: add const for rgbtoxyz matrix return

[Øyvind Kolås <ok src gnome org>]

commit a1e3264547cc5974c5037980f87d0cd9337ba497
Author: Øyvind Kolås <pippin gimp org>
Date:   Wed Aug 30 17:57:12 2017 +0200

    extensions/gray: add const for rgbtoxyz matrix return

 extensions/grey.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/extensions/grey.c b/extensions/grey.c
index f997dd8..8df1dab 100644
--- a/extensions/grey.c
+++ b/extensions/grey.c
@@ -38,7 +38,7 @@ conv_rgbaF_linear_y8_linear (const Babl *conversion,unsigned char *src,
                              long           samples)
 {
   const Babl *space = babl_conversion_get_source_space (conversion);
-  double *rgbtoxyz = babl_space_get_rgbtoxyz (space);
+  const double *rgbtoxyz = babl_space_get_rgbtoxyz (space);
   const float RGB_LUMINANCE_RED_FLOAT = rgbtoxyz[3];
   const float RGB_LUMINANCE_GREEN_FLOAT = rgbtoxyz[4];
   const float RGB_LUMINANCE_BLUE_FLOAT = rgbtoxyz[5];
@@ -68,7 +68,7 @@ conv_rgbaF_linear_yF_linear (const Babl *conversion,unsigned char *src,
                              long           samples)
 {
   const Babl *space = babl_conversion_get_source_space (conversion);
-  double *rgbtoxyz = babl_space_get_rgbtoxyz (space);
+  const double *rgbtoxyz = babl_space_get_rgbtoxyz (space);
   const float RGB_LUMINANCE_RED_FLOAT = rgbtoxyz[3];
   const float RGB_LUMINANCE_GREEN_FLOAT = rgbtoxyz[4];
   const float RGB_LUMINANCE_BLUE_FLOAT = rgbtoxyz[5];
@@ -96,7 +96,7 @@ conv_rgbaF_linear_yaF_linear (const Babl *conversion,unsigned char *src,
                               long           samples)
 {
   const Babl *space = babl_conversion_get_source_space (conversion);
-  double *rgbtoxyz = babl_space_get_rgbtoxyz (space);
+  const double *rgbtoxyz = babl_space_get_rgbtoxyz (space);
   const float RGB_LUMINANCE_RED_FLOAT = rgbtoxyz[3];
   const float RGB_LUMINANCE_GREEN_FLOAT = rgbtoxyz[4];
   const float RGB_LUMINANCE_BLUE_FLOAT = rgbtoxyz[5];