Marked functions parameters that are allowed to be NULL. Some APIs were also changed. The non-obvious APIs where NULL parameter was changed to "" are master_service_init() and auth_master_user_list_init(). These checks can currently be enabled only on a patched clang: http://llvm.org/bugs/show_bug.cgi?id=6786

Added support for a simplified IPC infrastructure. The idea is that you have one "ipc" proxy process, where all server processes connect to. IPC clients can then connect to the proxy and ask it to forward commands to either a specific server or all servers. The proxy does this, and forwards back any replies from the server.