Add ROA net_addr to grammar

Example:
  protocol static
  {
    route 10.110.0.0/16 max 16 as 1000 blackhole;
    route 10.120.0.0/16 max 24 as 1000 blackhole;
    route 10.130.0.0/16 max 24 as 2000 blackhole;
    route 10.130.128.0/18 max 24 as 3000 blackhole;
    ...
  }