[gcr] tests: Add missing const qualifier

[Stefan Walter <stefw src gnome org>]

commit d3935af8dd8fa48c1dfcde763698faf43bba8c82
Author: Philip Withnall <philip tecnocode co uk>
Date:   Tue Dec 6 07:50:56 2016 +0000

    tests: Add missing const qualifier
    
    This fixes a compiler warning.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=775685

 gcr/test-secure-memory.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gcr/test-secure-memory.c b/gcr/test-secure-memory.c
index f1a7a1f..7ef5b2f 100644
--- a/gcr/test-secure-memory.c
+++ b/gcr/test-secure-memory.c
@@ -141,7 +141,7 @@ test_alloc_oversized (void)
 static void
 test_realloc (void)
 {
-       gchar *str = "a test string to see if realloc works properly";
+       const gchar *str = "a test string to see if realloc works properly";
        gpointer p, p2;
        gsize len;