Make introspection work for zonesystem

... by skipping array size declarations and just letting the compiler
calculate the values for us using sizeof magic.
Deflicker: mode switching: gui complete
DEFLICKER_MODE_SOURCEFILE is working?
Deflicker "Automatic" is working?
IOP Exposure: histogram - when mode is automatic, change target level
Make sure deflicker will work only for raws (at least for now)
Some fixes for issues from hanatos review
Refactor histogram-related things a bit
Note that commit_params_late is less safe than commit_params
Rework lock release
Merge pull request #536 from LebedevRI/iop-exposure-deflicker-update

IOP Exposure - deflicker update
Merge branch 'master' of https://github.com/darktable-org/darktable
lua: prevent negative index of magic tables from working when they shouldn't
lua : always add an empty uservalue to all instances of dt types
lua.debug : prevent expanding _G and _ENV

this avoids flooding debug output by pulling the kitchen sink
lua debug : add a few more parameters

dt.debug.max_depth : how far recursion is allowed to go
dt.debug.known : allow to skip the documentation of some nodes
Merge branch 'master' of https://github.com/darktable-org/darktable
Translating in french and proof reading of chapter 3 of usermanual of darktable 1.5 till 3.2.4
	modified:   ../doc/usermanual/po/fr.po