Clarify server/d/<D>.z description

Spell out that fingerprints in requests should use capital A-F letters for their hex


svn:r6092

doc/dir-spec.txt

@@ -321,7 +321,7 @@ $Id$
    provide a unique descriptor to a client, and thereby partition that client
    from the rest of the network.)
 
-   The descriptor for a server whose digest (in hex) is <D> should be
+   The server descriptor with (descriptor) digest <D> (in hex) should be
    available at:
       http://<hostname>/tor/server/d/<D>.z
 
@@ -345,6 +345,10 @@ $Id$
    Directory servers MAY generate either format: the former requires less
    CPU, but the latter requires less bandwidth.
 
+   Clients SHOULD use upper case letters (A-F) when base16-encoding
+   fingerprints.  Servers MUST accept both upper and lower case fingerprints
+   in requests.
+
 5. Client operation: downloading information
 
    Every Tor that is not a directory server (that is, clients and ORs that do