r3140, r3144, r3298, r3299, r3300, r3307, r3308 merge: resolver fixes: *) fix memory leak in resolver *) fix resolver cache rbtree comparison *) fix segfault in resolver: ngx_resolve_name_done() and ngx_resolve_addr_done() did not delete contexts from a resolver node waiting list. *) fix "PTR ." case in address resolver *) add quotes in an error message, *) fix resolving an empty name (".") *) use ngx_resolver_alloc() instead of ngx_resolver_calloc() since all fields are filled