load unload lload lunload: Fix for areas starting with a digit

load unload lload lunload: Fix for areas starting with a digit

load and lload skip foreign ships unless explicitly named, and
suppress some error messages for ships not explicitly named.  Makes
sense, except the check for "explicitly named" is flawed: it checks
whether the argument starts with a digit.  Works as intended for lists
like 1/2/3.  Broken for areas that happen to start with a digit, such
as 0:9,0:5.  Visible in the load-tend test.

Screwed up when the feature was added in Empire 2.

Fix the obvious way: test for NS_LIST instead.  While there, drop the
p && *p guard, because it's always true after snxtitem().

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>