Implement P0599: 'noexcept for hash functions'. Fix a couple of hash functions (optional<T> and unique_ptr<T>) which were mistakenly marked as 'noexcept'. Reviewed as https://reviews.llvm.org/D31234

llvm-svn: 298573
diff --git a/libcxx/test/std/utilities/optional/optional.hash/hash.pass.cpp b/libcxx/test/std/utilities/optional/optional.hash/hash.pass.cpp
index ea89dc3..8f94d6b 100644
--- a/libcxx/test/std/utilities/optional/optional.hash/hash.pass.cpp
+++ b/libcxx/test/std/utilities/optional/optional.hash/hash.pass.cpp
@@ -36,6 +36,7 @@
     {
         typedef int T;
         optional<T> opt;
+        ASSERT_NOT_NOEXCEPT(std::hash<optional<T>>()(opt));
         assert(std::hash<optional<T>>{}(opt) == nullopt_hash);
         opt = 2;
         assert(std::hash<optional<T>>{}(opt) == std::hash<T>{}(*opt));
@@ -43,6 +44,7 @@
     {
         typedef std::string T;
         optional<T> opt;
+        ASSERT_NOT_NOEXCEPT(std::hash<optional<T>>()(opt));
         assert(std::hash<optional<T>>{}(opt) == nullopt_hash);
         opt = std::string("123");
         assert(std::hash<optional<T>>{}(opt) == std::hash<T>{}(*opt));
@@ -50,6 +52,7 @@
     {
         typedef std::unique_ptr<int> T;
         optional<T> opt;
+        ASSERT_NOT_NOEXCEPT(std::hash<optional<T>>()(opt));
         assert(std::hash<optional<T>>{}(opt) == nullopt_hash);
         opt = std::unique_ptr<int>(new int(3));
         assert(std::hash<optional<T>>{}(opt) == std::hash<T>{}(*opt));