Add -Wsign-promo to the hash test compile flags since I'm now trying to avoid the warning. I still need to check that it won't break older versions of gcc.

[SVN r38565]

libs/functional

@@ -1 +1 @@
-Subproject commit e5e8814e120f7b3a3fc18fb8fff9e764335f1eec
+Subproject commit bb774728a02b20545d67be42a09282142675aa05