Bug 31933

When pw is given a non-existenent numeric username as part of a delete, print
or modify command, it will interpret that username as a uid.  This occurs even
if the username was expliclity set using the -n argument.  This occurs because
the -n argument is overloaded.  It can be used both explicitly, and implicitly
for the initial username/uid argument.

Fix: This is a patch to the CVS version of pw.  It changes the implicit argument
prepended to the initial name/uid argument from "-n" to "--".  "--" is an
illegal argument on the command line, so by using it here, we avoid 
overloading any of our user given arguments.  Besides removing the 
overloading from the "-n" argument, we also make sure that we only do the 
name->uid conversion if we need to and if the "--" argument isn't NULL.

cvs server: Diffing .
How-To-Repeat: 
root@red# pw useradd -n testpw -u 41001
root@red# id testpw
uid=41001(testpw) gid=41001(testpw) groups=41001(testpw)
root@red# id 41001
uid=41001(testpw) gid=41001(testpw) groups=41001(testpw)
root@red# pw userdel -n 41001
root@red# id testpw
id: testpw: no such user
root@red# id 41001
id: 41001: no such user