Update hash documentation:

Rename to Boost.Functional/Hash. Add some extra details to the library header.
Use macros to link functions & classes.
Add a note about a couple of portability issues.


[SVN r28373]

libs/functional

@@ -1 +1 @@
-Subproject commit c1214408409fb41c5f50fb053a4572a561e9bb94
+Subproject commit 8da0e0104628704f52a71cd4f3682e8ed9776e05