Add gencode and genconfig

These files are used during the build process to generate
source files. They are temporary moved from ep_engine to
memcached to simplify the build process. They might be moved
back to ep_engine at a later time.

Change-Id: Iba1c07d35e84d441335806f384eda760d2690477
Reviewed-on: http://review.couchbase.org/29498
Tested-by: Trond Norbye <trond.norbye@gmail.com>
Reviewed-by: Michael Wiederhold <mike@couchbase.com>