Documentation/kernel-docs.txt: Add 4 paper/book references

Background/Reasoning:

Books:
------
 * Linux Kernel Networking by Rami Rosen
   While some parts are quite short and could be
   more carefully explained it's still a good recomendation
   for understanding linux kernel networking, (IMHO)

* Linux Treiber entwickeln:
  It sure is a drawback that this is a german book.
  But it's quite recent, well structured and there are also
  other non-english (spanish) books/papers in this list.

Papers:
-------

  * On Submitting kernel Patches
    Contains 2 case studies of bigger patch sets and how (or how not)
    they were merged. I found it helpful

  * Tracing the Way of Data in a TCP Connection through the Linux Kernel
    Since this was written by me this inclusion may be a bit biased :p
    Neitherless I think this gives a good introduction on
    understanding/exploring linux internals using ftrace and an overview
    of Linux TCP internals.

[mchehab@s-opensource.com: rebased to apply before rename]

Signed-off-by: Richard Sailer <richard@weltraumpflege.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>