Clarify that CPAN is not itself an authority

Also explain that "standard Perl 6 library" does not just mean
publicly shared libaries.

S11-modules.pod

@@ -8,8 +8,8 @@ Synopsis 11: Compilation Units
 
     Created: 27 Oct 2004
 
-    Last Modified: 28 Mar 2015
-    Version: 44
+    Last Modified: 2 Apr 2015
+    Version: 45
 
 =head1 Overview
 
@@ -393,11 +393,15 @@ Other than that, the semantics are identical to the direct form.
 
 =head1 Versioning
 
-Compilation units posted to an authority (such as CPAN) as part of a
-distribution, or entered into any standard Perl 6 library, are required to
-declare their full name so that installations can know where to keep them,
-such that multiple versions by different authors can coexist, all of them
-available to any installed version of Perl.
+Whenever an authority (such as a CPAN author or a company) posts a
+compilation unit as part of an official distribution, or enters it into
+any standard Perl 6 library, the module is required to declare its full
+name so that installations can know its unique, immutable identity,
+such that multiple versions by different authors can coexist, all of
+them available to any installed version of Perl.  (For the purposes of
+"standard Perl 6 library" we do not just mean publicly shared libraries
+such as CPAN, but also any internal or site-wide libraries that are
+shared outside the given module's dev group.)
 
 Such modules are also required to specify exactly which version (or
 versions) of Perl they are expecting to run under, so that future