K: is for keyword.  Syntax is perl extended regex.

Reorganized header documentation and indent the section entry descriptions
so that the first K: would not be considered a regex to match by
get_maintainer.pl
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>