Incorrect and inconsistent printing of unnamed class in the HTML generator

[mizvekov]

The HTML generator has some odd behavior with printing unnamed entities, which is not seen in the XML generator.

For example, for a test case such as:

constexpr struct
{
    void operator()() const;
} const F{};

It will list the class as Unnamed struct in the reference section, and the variable F will be given the following synopsis:
struct Unnamed struct;.

In the data members section, F will be given the following synopsis:
constexpr F = {};