(proced-descend): New variable.
(proced-sort): New arg descend.
(proced-sort-interactive): Repeated calls toggle sort order.
- (proced-format): Accomodate changes of proced-format-alist.
+ (proced-format): Accommodate changes of proced-format-alist.
Undefined attributes are displayed as "?".
(proced-process-attributes): New optional arg pid-list.
Ignore processes with empty attribute list.