Documentation: PM: Adjust freezing-of-tasks.rst to the freezer changes

The core freezer logic has been modified by commit f5d39b020809
("freezer,sched: Rewrite core freezer logic"), so adjust the
documentation to reflect the new code. The main changes include:

- Drop references to PF_FROZEN and PF_FREEZER_SKIP
- Describe TASK_FROZEN, TASK_FREEZABLE and __TASK_FREEZABLE_UNSAFE
- Replace system_freezing_cnt with freezer_active
- Use a different example for the loop of a freezable kernel thread,
since the old code is gone gone

Signed-off-by: Kevin Hao <haokexin@gmail.com>
[ rjw: Subject and changelog edits, doc text adjustments ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Documentation: Replace lkml.org links with lore

Replace the lkml.org links with lore to better use a single source
that's more likely to stay available long-term.

Done by bash script:

cvt_lkml_to_lore ()
{
tmpfile=$(mktemp ./.cvt_links.XXXXXXX)

header=$(echo $1 | sed 's@/lkml/@/lkml/headers/@')

wget -qO - $header > $tmpfile
if [[ $? == 0 ]] ; then
link=$(grep -i '^Message-Id:' $tmpfile | head -1 | \
sed -r -e 's/^\s*Message-Id:\s*<\s*//' -e 's/\s*>\s*$//' -e 's@^@https://lore.kernel.org/r/@')
# echo "testlink: $link"
if [ -n "$link" ] ; then
wget -qO - $link > /dev/null
if [[ $? == 0 ]] ; then
echo $link
fi
fi
fi

rm -f $tmpfile
}

git grep -P -o "\bhttps?://(?:www.)?lkml.org/lkml[\/\w]+" $@ |
while read line ; do
echo $line
file=$(echo $line | cut -f1 -d':')
link=$(echo $line | cut -f2- -d':')
newlink=$(cvt_lkml_to_lore $link)
if [[ -n "$newlink" ]] ; then
sed -i -e "s#\b$link\b#$newlink#" $file
fi
done

Link: https://lore.kernel.org/patchwork/patch/1265849/#1462688
Signed-off-by: Joe Perches <joe@perches.com>
Link: https://lore.kernel.org/r/77cdb7f32cfb087955bfc3600b86c40bed5d4104.camel@perches.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

PM: Wrap documentation to fit in 80 columns

Wrap to 80 columns. No textual change except to correct some "it's" that
should be "its".

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

docs: power: convert docs to ReST and rename to *.rst

Convert the PM documents to ReST, in order to allow them to
build with Sphinx.

The conversion is actually:
- add blank lines and indentation in order to identify paragraphs;
- fix tables markups;
- add some lists markups;
- mark literal blocks;
- adjust title markups.

At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Mark Brown <broonie@kernel.org>
Acked-by: Srivatsa S. Bhat (VMware) <srivatsa@csail.mit.edu>