/*
 * Get the width and height of the given string using this font.
 *
 * Example:
 *   font = Imlib2::Font.new 'helvetica/12'
 *   size = font.size 'how big am i?'
 *   ['width', 'height'].each_index { |i, v|
 *     puts 'text ' << v << ' = ' << size[i]
 *   }
 *
 */
static VALUE font_text_size(VALUE self, VALUE text) {