New process port exchange changed. READY message type introduced.

Application process start request DATA message from router to master.
Master notifies router via NEW_PORT message after worker process become ready.

src/nxt_port_memory.h

@@ -15,6 +15,8 @@ typedef struct nxt_port_mmap_header_s nxt_port_mmap_header_t;
 void
 nxt_port_mmap_destroy(nxt_port_mmap_t *port_mmap);
 
+void nxt_port_mmaps_destroy(nxt_array_t *port_mmaps, nxt_bool_t destroy_pool);
+
 /*
  * Allocates nxt_but_t structure from port's mem_pool, assigns this buf 'mem'
  * pointers to first available shared mem bucket(s). 'size' used as a hint to