memcached: fix doc section IDs, copy and paste error from dmq
memcached: add new parameter 'stringify', patch from Federico Cabiddu
* add a new parameter 'stringify' to the memcached module to force the module
  to evaluate all returned values as strings. This is useful if other parts
  of the memcached infrastructure are not able to set the correct value flags
* patch from Federico Cabiddu, federico dot cabiddu at gmail dot com
* add documentation for the new parameter