opencl: in debug mode tell user dt was built without opencl support
(cherry picked from commit d5e4b1d8bba3a881fd7de4e3dffb0216859d22ac)
Don't allow going to DT_MODE_NONE with key accels
don't erase blend_params on  module version update
lowpass: add lightness control
Make it possible to translate lightness with context.

Here we are not talking about HSL lightness. Needed for French translation.
Update French translation for lowpass module.
Merge branch 'lowpass-translation'

* lowpass-translation:
  Update French translation for lowpass module.
  Make it possible to translate lightness with context.
pfm: move fallback date/time initialization to exif reading time.

this way it'll be done on import, not on thumbnail loading time.