/*
 * Set the size (in bytes) of the application-wide font cache.
 * Examples:
 *   new_size = 8 * 1024 ** 2                # 8 megabytes
 *   Imlib2::Cache::set_font_cache new_size
 *
 *   new_size = 8 * 1024 ** 2                # 8 megabytes
 *   Imlib2::Cache::font_cache = new_size
 *
 *   new_size = 8 * 1024 ** 2                # 8 megabytes
 *   Imlib2::Cache::font = new_size
 */
static VALUE cache_set_font(VALUE klass, VALUE val) {