New -u option: fetch updates to installed pacakges.

Sort options in man page.
Make it clear -a and -u are instead of naming packages on the command
line.

Similarly -i -g -x are pointless with -a or -u, and -a is mutually
exclusive with -u
Add updates_for_installed with corresponding -u option.

Sort options.  Sort option letters in getopts() and fetch_usage().
Update usage to show -a and -u are instead of naming packages, and -a
is mutually exclusive with -u.

Make variable declarations line up stylishly.
Add a flag to control if the pkg version test is done: it isn't wanted
when we're just querying for available upgrades in order to fetch the
pkgs.

I don't see why the whole version testing thing exists at all: pkg
forcing itself to run first shouldn't be necessary.
Improve the jobs summary list of what has to be fetched
Fixes issue #409: Download pkgs needed for all the upgradable packages
on a machine

When querying the repo for the size and version of pkgs to download,
these should be stored as *newversion* and *newflatsize*

Show what %age of each pkg there is still to download.