prima text properties and getters

The following text-based getters need to be implemented:

prima_get_text_widths, prima_get_text_boxes, prima_get_font_abcs

Each of those take a number of text properties that need to be supported, including name, height, size, width, style, and pitch, which are also important for texts_out and (probably) draw_texts. More research is needed for this, so add comments!
