Ignore MALLOC_CONF in set{uid,gid,cap} binaries.

This eliminates the malloc tunables as tools for an attacker.

Closes #173

include/jemalloc/internal/jemalloc_internal_defs.h.in

@@ -66,6 +66,16 @@
  */
 #undef JEMALLOC_OSSPIN
 
+/*
+ * Defined if secure_getenv(3) is available.
+ */
+#undef JEMALLOC_HAVE_SECURE_GETENV
+
+/*
+ * Defined if issetugid(2) is available.
+ */
+#undef JEMALLOC_HAVE_ISSETUGID
+
 /*
  * Defined if _malloc_thread_cleanup() exists.  At least in the case of
  * FreeBSD, pthread_key_create() allocates, which if used during malloc