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/test/meson.build b/test/meson.build
index 98435bf..ab788ff 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -4,6 +4,7 @@
   'handle/copyable': [stdplus_dep, gtest_main_dep],
   'handle/managed': [stdplus_dep, gtest_main_dep],
   'hash': [stdplus_dep, gtest_main_dep],
+  'hash/tuple': [stdplus_dep, gtest_main_dep],
   'pinned': [stdplus_dep, gtest_main_dep],
   'raw': [stdplus_dep, gmock_dep, gtest_main_dep],
   'signal': [stdplus_dep, gtest_main_dep],