(org-open-file): Use mailcap for selecting an

(org-open-file): Use mailcap for selecting an
	application.
	(org-file-apps-defaults-gnu): Use mailcap as the default for
	selecting an application on a UNIX system.
	(org-agenda-show-tags): New command.
	(org-table-insert-hline): Keep cursor in current table
	line.
	(org-table-convert): Offset effect of modifying
	`org-table-insert-hline'.
	(org-format-agenda-item): New optional argument TAG.
	(org-compile-prefix-format): Handle %T format for the tag.
	(org-expand-wide-chars): New function.
	(org-table-insert-row, org-table-insert-hline): Use
	`org-expand-wide-chars'.
	(org-open-file): Fixed bug in program launch.
	(org-get-time-of-day): Fixed bug with times before 1am.
	(org-agenda-menu): Addes tags commands.