Add note about libmemcached version

diff --git a/doc/book.xml b/doc/book.xml
index 2107746..403bc9c 100644 (file)
--- a/doc/book.xml
+++ b/doc/book.xml
@@ -702,6 +702,7 @@
        for result-set caching for ZOOM.
        The prefix can not be given. Note that YAZ will only search
        for libMemcached if Libgcrypt is also enabled.
+       Note that 0.40 of libmemcached is required.
        </para>
        </listitem>
       </varlistentry>