Mangle the names of internal classes so they're less likely to conflict with derived class names and members.

Fixes #4453.

[SVN r64251]

libs/type_traits

@@ -1 +1 @@
-Subproject commit 4588039349e5e2359f0dfe0195c907d71e063dca
+Subproject commit c9406a97fe68c75bcb4802c28169d78f0b294c3c