Build with memcached >= 1.0.9

A commit to make php-memcached build against libmemcached >= 1.0.9 (tested with 1.0.17). Unfortunately libmemcached broke API on a minor release, so we have to do #ifdef trickery. You might be better off asking libmemcached to provide some backwards compatibility, but here's the patch anyway.

Along with that, a couple of minor semi-unrelated commits.