standalone_edc overflows the stack

This is visible in a package build, not a plain from source build as the debian packaging adds -fstack-protection and -fstack-protection-strong (or something like that) to the build.

This was tracked down to the boost::lock_free queue api, the spsc (single producer/single consumer) queue. This is used to pass diagnostic information between the main epics thread and the network server that can give a dump of all the channels that are not currently connected. Upon investigation it was found that the api is suprising, the pop call when given a pointer will copy all available entries to the pointer, instead of a single entry. This is good in that it can allow efficient clearing of the queue, but surprising if you are not expecting this.