[FEATURE REQUEST] API to query available font families and styles

[peterhorvath111]

In Arnold we use OIIO to render text over our rendered images. We have a user interface where end users can configure text render, such as specify the font, font size, alignment, etc. They can select the font from a combo box that lists available font familes (e.g. "Arial", "times New Roman", etc.) and styles (e.g. "Regular", "Bold", "Italic", etc).

Therefore we extended the API to return available font families and styles per family. If you think this would be interesting to have, we can port our code back.