Memcached PHP client improvements

Memcached PHP client improvements

* When there is a read error, close the socket and mark the server dead,
  instead of continuing to send requests through it, causing a protocol
  violation.
* Also check for write errors.
* Increase the default stream and connect timeouts from 100ms to 500ms.
* Remove the commented-out _safe_fwrite() code that I wrote in 2005,
  that PHP bug is fixed now, so writes can be handled the same way as
  reads.
* Fix E_STRICT errors in get_multi() due to a resource being used as an
  array index.
* For performance, flush the read buffer less often (only on persistent
  connect).
* Move the fread() loop from _load_items() into its own new function.
* Be stricter about stripping expected newlines, don't just run trim() on
  everything.
* Make MemCachedClientforWiki into a simple alias since the distinction
  with MWMemcached was lost many years ago. We even renamed the class
  "MWMemcached".
* Remove vim modeline made incorrect by 19d6293 (Nov 2009).

Change-Id: I81de31049b87038999e37054d8d174a782c78a68