HPCC-11522 libmemcached plugin

Signed-off-by: jamienoss <james.noss@lexisnexis.com>
I would have liked to compress this list yes. I didn't know how to get round ECL not allowing function overloading - I think I discussed this with you. Can you use templates or a macro in a SERVICE def, or do so outside? I also thought about just having i8 & r8 but thought that the user would want to be able to control mem sizes.