compiler warning fixes


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@1824 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/include/vg_skin.h b/include/vg_skin.h
index 2dc221a..1d94ee0 100644
--- a/include/vg_skin.h
+++ b/include/vg_skin.h
@@ -441,8 +441,8 @@
                                    __PRETTY_FUNCTION__), 0)))
 
 __attribute__ ((__noreturn__))
-extern void VG_(skin_assert_fail) ( Char* expr, Char* file, 
-                                    Int line, Char* fn );
+extern void VG_(skin_assert_fail) ( const Char* expr, const Char* file, 
+                                    Int line, const Char* fn );
 
 
 /* ------------------------------------------------------------------ */