Add 'acronyms as ordinary words' guideline

[SVN r15991]

more/lib_guide.htm

@@ -173,8 +173,9 @@ library, but a reasonable effort to comply is expected.</p>
 <ul>
   <li>Use the lowercase/underscore <a href="#Naming">naming conventions</a> of
     the C++ standard library.&nbsp; Template parameter names begin with an
-    uppercase letter. Macro (gasp!) names should be all uppercase and begin with
-    BOOST_.</li>
+    uppercase letter. Macro (gasp!) names should be all uppercase and begin with 
+    BOOST_. Acronyms should be treated as ordinary words 
+    (e.g. <code>xml_parser</code> instead of <code>XML_parser</code>). </li>
 </ul>
 <ul>
   <li>Choose meaningful names - explicit is better than implicit, and readability counts.