[LUAU] clarifications

[Rob Braun]

Nitpicking starting here, sorry about this.  I just noticed                    
some points in the thread that could use some clarification.                    
                                                                                
Yup, there is a difference between UNIX and Linux.  Kindof.                     
Not really, though.  UNIX (the AT&T piece of software, the                      
patent originally being set uid execution, and currently owned                  
by Novell) does not exist as such anymore.  There are kind of                   
two definitions, the general family of unix like operating systems,             
and the original API implemented by AT&T UNIX.  Linux implements                
the original API from the point of view of the application, with                
many extentions.  It does not use the same abstraction system                   
internally.  An example would be the BSD sockets that got integrated            
into AT&T UNIX, uses mbuff's to describe data recieved over a                   
network, or even internally.  Linux uses skbuff's.  There are                   
subtle differences between the two.                                             
Anyway.  Within the family of operating systems refered to as UNIX,             
there is quite a bit of variation.  If one considers Berkeley UNIX              
to be in that family, as most do, there are substantial differences.            
Compare Solaris 7 to HPUX 11 to OpenBSD 2.5.  Huge variation in                 
file organization, startup scripts, directory structure, kernel                 
configuration, etc.  So, given this widely varying family of operating          
systems, Linux is not much different to the user or application                 
programmer.                                                                     
There are a lot of differences to the kernel hacker, though.                    
And even the application programmer, where one must be aware of                 
the internal kernel structures, will notice large differences.                  
                                                                                
So, when someone or something says "I support UNIX and Linux",                  
there is some difference, but usually not enough of one to justify
the distinction.  

Another point is on the hosts.allow thread.  hosts.allow and hosts.deny
come from Weitse Venema's tcpwrappers package.  The current version,
last I checked about a month ago, was 7.6.  Many linux distributions 
ship with 7.5.  Starting with version 7.6, the syntax is expanded and
much more flexible, but is incompatible with version 7.5 and earlier.
So, when talking about syntax of hosts.allow and hosts.deny, it is
useful to give which version of tcpwrappers you are using, as someone
may give you syntax that is incorrect for your version.

Rob
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