Improve support for generic constraints

[yeputons]

E.g. HTMLCollectionOf<> returned by getElementsByClassName

[stheophil]

• Generate templates for generic classes
• Generate non-type templates for generics with enum/double non-type parameters
• Generate basic type constraints in C++ such as std::is_base_of<Node, T> for interface A<T extends Node>

[stheophil]

• Update tree of parsed classes, functions, variables so they store back pointers to their parents.
• Lookup TypeParameters in type parameter collections of each parent to resolve type parameter to their type. See MangleVariableTypeParameterAsType

[stheophil]

For IndexedAccessTypes, something like this with boost::Hana could be nice:

#include <functional>
#include <boost/hana/assert.hpp>
#include <boost/hana/integral_constant.hpp>
#include <boost/hana/map.hpp>
#include <boost/hana/pair.hpp>
#include <boost/hana/type.hpp>
#include <boost/hana/string.hpp>
#include <boost/hana/hash.hpp>
#include <boost/hana/at_key.hpp>

#include <string>
using namespace std::literals;
namespace hana = boost::hana;

struct SChangeEvent {};
struct SMouseEvent {};

static constexpr auto m = hana::make_map(
    hana::make_pair(BOOST_HANA_STRING("change"), hana::type_c<SChangeEvent>),
    hana::make_pair(BOOST_HANA_STRING("mousemove"), hana::type_c<SMouseEvent>)
);
template<typename T> 
void addEventListener(T t, std::function<void(typename decltype(+m[t])::type)>);

int main() {
    std::function<void (SChangeEvent)> fn;
    addEventListener(BOOST_HANA_STRING("change"), fn);
}

[stheophil]

Slightly better error message with

template<typename T, typename Arg, 
    std::enable_if_t<
        // hana::contains(hana::keys(m), T{}) &&
        std::is_same_v<Arg, typename decltype(hana::find(m, T{}))::type>
    >* = nullptr 
> 
void addEventListener(T t, std::function<void(Arg)>);

[stheophil]

IndexesAccessTypes supported in commit 9eb2f9b