* doc/manuals/abidiff.rst: Add documentation for the new
--suppressions command line switch.
(--harmless, --harmful): Refer to the new "concepts" section
below, where harmful/harmless concepts are now explained.
(Notes): Move the content of the notes section where
harmful/harmless concepts were explained, to the newly created
'Concepts' section.
* doc/manuals/index.rst: Limit the depth of the table of content
to 2. Add the new libabigail-concepts.rst stuff in here. Adjust
for the renaming of tools.rst to libabigail-tools.rst.
* doc/manuals/libabigail-concepts.rst: New file.
Signed-off-by: Dodji Seketeli <dodji@redhat.com>
