Added Windows syntax for first "cd" command mention.

doc/xdocs/building.html

@@ -51,7 +51,7 @@
 	<a href="http://acegisecurity.sourceforge.net">http://acegisecurity.sourceforge.net</a>).
 	In this case, execute:</p>
   <ol>
-	<pre>cd $ACEGI_SECURITY/core</pre>
+	<pre>cd $ACEGI_SECURITY/core (or cd %ACEGI_SECURITY%/core on Windows)</pre>
 	<pre>maven jar:install</pre>
 	<pre>cd $ACEGI_SECURITY/samples/contacts</pre>
 	<pre>maven multiwar:multiwar</pre>