Clarify that you need ActiveState perl 5.8 *or later* to build on Windows.

Author: hlinnaka

doc/src/sgml/install-win32.sgml

@@ -83,7 +83,7 @@
       ActiveState Perl is required to run the build generation scripts. MinGW
       or Cygwin Perl will not work. It must also be present in the PATH.
       Binaries can be downloaded from
-      <ulink url="http://www.activestate.com"></> (Note: version 5.8 is required,
+      <ulink url="http://www.activestate.com"></> (Note: version 5.8 or later is required,
       the free Standard Distribution is sufficient).
      </para></listitem>
     </varlistentry>