memcached FAQ links to obsolete binary protocol doc

[Mat Hostetter]

The memcached FAQ links to this document describing the binary protocol:

    http://code.google.com/p/memcached/wiki/MemcacheBinaryProtocol

Unfortunately, this document is out of date compared to the
protocol-binary.xml that ships with 1.4.0.  For example, it is missing
various opcodes like IncrementQ.  Now that 1.4.0 is out, it would be
good to update the protocol document on the wiki.

-Mat