Make some variables and functions static when not used outside of a module.
Make variables in headers extern.
Delete the unused db_find_watchpoint() function.
- sort entries in the various command tables, so that the `help' lists
are easier to use. this included hacking db_machine_commands_install()
to search for the "machine" entry to change the `more cmds' pointer,
rather than assuming it was the first entry
- add a `sync' command, which is effectively `reboot 0x100'.
- remove db_help_cmd(); it was unused (and was almost a duplicate of
db_cmd_list()).
- move some extern decls to db_output.h, since they're used in more than one
place now
- rename NEXT_TAB to DB_NEXT_TAB and move to db_output.h
