Add a bunch of noexcepts to char_traits and string_view.

llvm-svn: 276955
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: aa849bc2f23432af3104b2c1524009312bcad223
diff --git a/include/string_view b/include/string_view
index 08fcfd6..67fc606 100644
--- a/include/string_view
+++ b/include/string_view
@@ -356,7 +356,7 @@
 	}
 
 	_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-	int compare(const _CharT* __s) const
+	int compare(const _CharT* __s) const _NOEXCEPT
 	{
 		return compare(basic_string_view(__s));
 	}