functions to return data about an image.
* packet.h, parse-packet.c (make_attribute_uidname,
parse_attribute_subpkts, parse_attribute), photoid.h, photoid.c
(show_photos): Handle multiple images in a single attribute packet.
* main.h, misc.c (pct_expando), sign.c (mk_notation_and_policy), photoid.c
(show_photos): Simpler expando code that does not require using
compile-time string sizes. Call image_type_to_string to get image strings
(i.e. "jpg", "image/jpeg"). Change all callers.
* keyedit.c (menu_showphoto), keylist.c (list_keyblock_print): Allow
viewing multiple images within a single attribute packet.
* gpgv.c: Various stubs for link happiness.
