Inform ProXL that Font is no longer being "held onto" by the programmer. As soon as no gcs refer to it, Font will be unloaded.

Warning: A font is considered to be "held onto" when it is created, or when it is got from a gc (e.g., by get_graphics_attributes). It is the responsibility of the programmer to ensure that she is not releasing a font that is being held by another branch of her code. For example, If a font is created, asserted somewhere, and put into a gc, and later is accessed through the gc, the programmer must not release it at this point, since it is still in the database and may be used. Be careful.