Fix some casts that removed const-ness as pointed out by
GCC's -Wcast-qual.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13138 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/memcheck/mc_malloc_wrappers.c b/memcheck/mc_malloc_wrappers.c
index 5b967b0..336693c 100644
--- a/memcheck/mc_malloc_wrappers.c
+++ b/memcheck/mc_malloc_wrappers.c
@@ -669,8 +669,8 @@
 static Int 
 mp_compar(const void* n1, const void* n2)
 {
-   const MC_Chunk* mc1 = *(const MC_Chunk**)n1;
-   const MC_Chunk* mc2 = *(const MC_Chunk**)n2;
+   const MC_Chunk* mc1 = *(const MC_Chunk *const *)n1;
+   const MC_Chunk* mc2 = *(const MC_Chunk *const *)n2;
    if (mc1->data < mc2->data) return -1;
    if (mc1->data > mc2->data) return  1;
    return 0;