Introducing extended app process management.

- Pre-fork 'processes.spare' application processes;
- fork more processes to keep 'processes.spare' idle processes;
- fork on-demand up to 'processes.max' count;
- scale down idle application processes above 'processes.spare' after
  'processes.idle_timeout';
- number of concurrently started application processes also limited by
  'processes.spare' (or 1, if spare is 0).

src/nxt_conf.c

@@ -163,6 +163,13 @@ nxt_conf_get_string(nxt_conf_value_t *value, nxt_str_t *str)
 }
 
 
+int64_t
+nxt_conf_get_integer(nxt_conf_value_t *value)
+{
+    return value->u.integer;
+}
+
+
 nxt_uint_t
 nxt_conf_object_members_count(nxt_conf_value_t *value)
 {