Activate GUI for watermark layout.

It is now possible to layout properly a watermark whose scale is
computed based on the larger or smaller border. This make it possible
to use a watermark inside a style an apply it into images in portrait
and landscape mode with proper layout.
film strip: try to be thread safe while switching images.
usermanual: recommend to not use module in its current state
Merge branch 'master' of ssh://github.com/darktable-org/darktable
Update pt_BR translation
Merge pull request #204 from guitorri/update_pt_BR

Update pt_BR translation
Revert "film strip: try to be thread safe while switching images."

This reverts commit 683f827b4a64de71c6c3598c4c2fbcec35ed84ac.

didn't quite solve it.
pixelpipe: introduce mutices for pipelines while develop_t uses them.
darkroom: lock pixelpipes before destroying them.

should fix crashes/hangs when pressing spacebar like crazy.
[l10n] Swedish update
Fix aspect ratio computation.

It cannot happen in legacy_params() as at this point the size of the
image is not yet known. We then use a deferred circuitry to handle
this at the right point in the code.

Fixes #9320.
Merge branch 'fix-clipping-aspect'

* fix-clipping-aspect:
  Fix aspect ratio computation.
Preliminary update of the Russian translation
fix: denoiseprofile: also show "found match:" instead of the profile name for index 0
denoiseprofile: make it possible to copy the information "this profile was set automatically" across images with different ISO and camera vendor
denoiseprofile: only use a[0] = -1.0 to signal autodetection, and don't use epsilon for comparisons
noise profile: canon eos 1d iv by rene weiss
Merge pull request #206 from bluesceada/denoise-copy-autodetect

denoiseprofile: copy "profile autodetected" correctly + fix: display "found match" also for first profile
fix: denoiseprofile: crash when trying to update presets/styles from version 2 to 3
do not try to find autodetection for them - would probably be not useful and is impossible anyway
denoiseprofile: get param "mode" right when converting params from version 2 to 3