Add all the relational operators to std::experimental::optional. Also update bad_optional_access to match the Library Fundamentals draft standard. This is not all of the upcoming changes to optional, though.

llvm-svn: 223775
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: e61fba3b70949e2955f946b81a215c7e08d9aee6
diff --git a/src/optional.cpp b/src/optional.cpp
index b614d81..8c5dd76 100644
--- a/src/optional.cpp
+++ b/src/optional.cpp
@@ -9,8 +9,7 @@
 
 #include "experimental/optional"
 
-namespace std  // purposefully not using versioning namespace
-{ namespace experimental {
+_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
 
 #ifdef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
 
@@ -22,4 +21,4 @@
 
 #endif
 
-}}  // std::experimental
+_LIBCPP_END_NAMESPACE_EXPERIMENTAL