[PATCH] Add documentation about /proc/sys/vm/laptop_mode to various docs.

[PATCH] Add documentation about /proc/sys/vm/laptop_mode to various docs.

From: Bart Samwel <bart@samwel.tk>

A bunch of small laptop mode updates:

* Mention the laptop_mode and block_dump sysctls in the relevant docs,
  referring to the laptop-mode.txt. Improve description of what the
  laptop_mode knob means (i.e. seconds between last I/O and automatic
  sync).

* Document the most relevant config file options.

* Change the installation instructions in the laptop mode doc to describe
  the ACPI-bound version first, because this is the easiest. Explain
  the non-ACPI version afterwards. Added a reference to my "packaged
  version" of the scripts.

* Move the setting of hdparm and cpu frequency out of the ACPI script
  and into the core laptop mode script. Add config option DO_HD to
  enable hdparm. Add config setting HD to set device to do hdparm on.
  Rename Dax's CPU_MANAGE to DO_CPU, with 0/1 instead of yes/no, to
  improve consistency.

* Fix a problem where the root filesystem wouln't be remounted when
  /etc/mtab listed its type as "unknown". Deduce the type of "unknown"
  filesystems from /etc/fstab.

This depends on the patch that adds config files, which was submitted
to Linus by Dax Kelson on July 10.

Signed-off-by: Bart Samwel <bart@samwel.tk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>