Coccinelle: Improve user information with a new kind of comment

Improve user information with a new kind of comment
about semantic patch output.

Fix spelling.

Signed-off-by: Nicolas Palix <npalix.work@gmail.com>
Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Michal Marek <mmarek@suse.cz>