A few fixes to build under VS2013.

[tangent-vector]

The main changes are:

• Use enums instead of constexpr members in type-trait templates
• Manually deal with ambiguity between zero-arument default constructors and constructors that uses a parameter pack (which could be empty)
• Explicitly quality some references to CoreLib::Text::TokenType, because it is otherwise ambiguous with a symbol declared in a Windows header.