hash: Add support for tuples

There is now builtin support for stdplus::hash<> and
stdplus::hashMulti(...) hashing std::tuple containers.

Change-Id: I0e0983c04d54302f00c811e5de0d949accee03d7
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/src/meson.build b/src/meson.build
index c4662ad..ed994ea 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -48,6 +48,7 @@
   'handle/copyable.cpp',
   'handle/managed.cpp',
   'hash.cpp',
+  'hash/tuple.cpp',
   'pinned.cpp',
   'raw.cpp',
   'signal.cpp',