cacorrect: clamp the bottom end to zero
Update some osm-gps-map sources
(cherry picked from commit 6aa1f85896ee1dc29b1d57f4ccfe55b8c6da502b)
thumbnail compression: make libsquish optional.

some poor sobs in undeveloped countries are concerned by software patents.
(cherry picked from commit 1b9952c990c3611691306bfd46e0929c7fc14386)
highlights: fix some sharp borders and some magenta.
(cherry picked from commit 3b07ec4b217177250fcbbfc9b25bff58e48209d7)
wb_presets: sony slt-a37 (stolen from ufraw)
thumbnail compression: make libsquish default on, to be compatible with old behaviour.
(cherry picked from commit 2342d061d2f119ccce003cafddb65fe0de2eaca7)