Make OPT.String() more dig-like, Fix MBZ display

[brianshea2]

• Minor changes to how the OPT String() function generates its output to better match dig
  • colon after "version"
  • comma vs. semicolon
  • flags are space separated (no comma)
• The CO flag could be set without the DO flag
• Fix getting of the Z value

[brianshea2]

e := new(dns.OPT)
e.Hdr.Name = "."
e.Hdr.Rrtype = dns.TypeOPT
e.SetUDPSize(1400)
e.SetDo()
e.SetCo()
fmt.Println(e.String())

Before:

;; OPT PSEUDOSECTION:
; EDNS: version 0; flags: do, co; MBZ: 0x4000, udp: 1400

After:

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags: do co; udp: 1400

[miekg]

i think moving further away from the dig-format would be better, https://codeberg.org/miekg/dns does that.

no need to do it here.

[brianshea2]

@miekg this also fixes the currently broken display of the MBZ value. Are you no longer accepting fixes for this project?