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
lua : update usermanual generation
lua api usermanual : remove history information
lua usermanual : sanity checks on the database used to generate the manual
lua api : more reproducible documentation builds
lua usermanual API : reimplement attribute list according to upegelow's input
lua usermanual : remove <synopsis> to have proper linewrap

this doesn't look as good, i'll have to find a clean way to do it...
Merge pull request #541 from boucman/lua_usermanual

lua : update usermanual generation
colorin: don't warn about missing color matrix for non-raw images
Fix the strlen removal, blobs need a correct size

no idea why I changed those, obviously bogus.
Do not rotate data upon loading. We will rotate it later in flip IOP
Refactor bitwise orientation into enum dt_image_orientation_t
IOP Flip: take care of flipping