Updates to LTS/Development

[Guido Günther <agx@sigxcpu.org>]

Hi,
I've updated LTS/Development in the wiki a bit:

- document "postponed" and "ignored"
- clarify about security isssues in LTS affecting LTS+1, LTS+2 and sid
  as well.

  https://wiki.debian.org/LTS/Development?action=diff&rev2=151&rev1=150

I'd welcome any feedback, corrections.
Cheers,
 -- Guido