suppressed a false positive in libdl.

Author: agentzh

valgrind.suppress

@@ -447,4 +447,16 @@
  fun:ngx_palloc_block
  fun:ngx_palloc
 }
-
+{
+ <insert_a_suppression_name_here>
+ Memcheck:Cond
+ fun:index
+ fun:expand_dynamic_string_token
+ fun:_dl_map_object
+ fun:map_doit
+ fun:_dl_catch_error
+ fun:do_preload
+ fun:dl_main
+ fun:_dl_sysdep_start
+ fun:_dl_start
+}