Missing GetInt128Ty and GetIntNTy on LLVMSharp.Type

[retroandchill]

These APIs have analogues in the C-API, and currently there's no way to access the API I need.

This is the workaround I've come up with, but it's not ideal, so if this could be added to the public API, that would be great.

internal static class LlvmTypeHelpers
{
    extension(Type)
    {
        public static Type GetInt128Ty(LLVMContext context)
        {
            var typeRef = context.Handle.Int128Type;
            return context.GetOrCreate(typeRef);
        }
    }

    [UnsafeAccessor(UnsafeAccessorKind.Method, Name = "GetOrCreate")]
    private static extern Type GetOrCreate(this LLVMContext context, LLVMTypeRef typeRef);
}