bsdtar errors storing uid/gids > 16777214

It looks like bsdtar will create extended header entries for attributes
that would overflow the regular file header, but for the gid and uid
cases, it doesn't zero out the regular fields, and
__archive_write_format_header_ustar() ends up failing.  This bit me
when portupgrading kdebase, which installs kdesud with a group name of
"nogroup", which is -2 (aka 4294967294) on my system.

Also, there's a formatting error in tar/read.c that ends up misaligning
the date column.  %Y is 4 chars wide, but %R is 5, so the format string
with %R in it needs to lose a space.

-- 
	Dan Nelson
	dnelson_at_allantgroup.com