[gtk+/native-layout] Fix compilation warning: use const *gchar variable

[Tristan Van Berkom <tvb src gnome org>]

commit 02b2810a0e553e06f4e6245efa2dc25fd96c1d39
Author: Javier Jardón <jjardon gnome org>
Date:   Mon Jan 4 11:47:40 2010 +0100

    Fix compilation warning: use const *gchar variable
    
    https://bugzilla.gnome.org/show_bug.cgi?id=605090

 gtk/gtklabel.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtklabel.c b/gtk/gtklabel.c
index 35c236d..eb380fa 100644
--- a/gtk/gtklabel.c
+++ b/gtk/gtklabel.c
@@ -3850,7 +3850,7 @@ separate_uline_pattern (const gchar  *str,
                         gchar       **pattern)
 {
   gboolean underscore;
-  gchar *src;
+  const gchar *src;
   gchar *dest;
   gchar *pattern_dest;
 
@@ -3867,7 +3867,7 @@ separate_uline_pattern (const gchar  *str,
   while (*src)
     {
       gunichar c;
-      gchar *next_src;
+      const gchar *next_src;
 
       c = g_utf8_get_char (src);
       if (c == (gunichar)-1)