Document that shared_preload_libraries and local_preload_libraries

lowercase the library names, unless double-quoted.

doc/src/sgml/config.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.285 2010/06/28 22:46:11 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.286 2010/06/29 22:23:02 momjian Exp $ -->
 
 <chapter Id="runtime-config">
   <title>Server Configuration</title>
@@ -1015,6 +1015,7 @@ SET ENABLE_SEQSCAN TO OFF;
         <literal>mylib.so</> (or on some platforms,
         <literal>mylib.sl</>) to be preloaded from the installation's
         standard library directory.
+        All library names are converted to lowercase unless double-quoted.
         If more than one library is to be loaded, separate their names
         with commas.  This parameter can only be set at server start.
        </para>
@@ -4838,7 +4839,8 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
        <para>
         This variable specifies one or more shared libraries that are
         to be preloaded at connection start.  If more than one library
-        is to be loaded, separate their names with commas.
+        is to be loaded, separate their names with commas.  All library
+        names are converted to lowercase unless double-quoted.
         This parameter cannot be changed after the start of a particular
         session.
        </para>