[2/2]dwrite: basic implementation for FontCollectionLoader registration

[Nikolay Sivov]

> +    IDWriteFontCollectionLoader **CollectionLoaders;
> +    LONG CollectionLoaderCount;

I'd really like a better naming for those, something like 'loaders' and 
'loaders_count'.

> +    if (i == This->CollectionLoaderCount)
> +    {
> +        This->CollectionLoaderCount++;
> +        if (This->CollectionLoaders)
> +            This->CollectionLoaders = heap_realloc(This->CollectionLoaders, This->CollectionLoaderCount * sizeof(IDWriteFontCollectionLoader*));
> +        else
> +            This->CollectionLoaders = heap_alloc(This->CollectionLoaderCount * sizeof(IDWriteFontCollectionLoader*));
> +        if (!This->CollectionLoaders)
> +            return E_OUTOFMEMORY;
> +    }
> +    IDWriteFontCollectionLoader_AddRef(loader);
> +    This->CollectionLoaders[i] = loader;

This should grow more efficiently in my opinion. Also it probably makes 
sense to have small number of slots allocated on initial factory 
creation or even use a list (you don't need index access). Another 
question is do we want to register a default local loader on factory 
creation or not.