Freestyle: Fix typos in a tool tip.
Spelling error fixes
Fix T39880: Cancelling transforms in Graph Editor does not restore F-Curves to original state

Since autosnap was being applied during the flushing step for various practical reasons,
it wasn't possible to restore keyframes and handles to their original values, as these
would always get overwritten before getting a chance to be written back to the keyframes.
Fix T39886: Transformed parents of Rigid Bodies cause problems with Bake To Keyframes

Need to convert transforms to parent space for objects with parents.
Fix T38924: wm.link_append() could fail to append

When the library path was changed by BLI_cleanup_path
appending would fail.
Fix T39799: Backdrop (compositor) ignores alpha.

This issue is because of a somewhat "special" behavior in old code, which got lost during rB09874df:

There was a variant of the `relinkConnections` function which would leave the socket completely unconnected. This is not a valid state really (given that each unconnected input must otherwise connected to a constant `Set` type node), but was used as a way to distinguish connected alpha/depth sockets in composite and viewer output nodes.
https://developer.blender.org/diffusion/B/browse/master/source/blender/compositor/intern/COM_InputSocket.cpp;28a829893c702918afc5ac1945a06eaefa611594$69

After the large cleanup patch ({D309}) every socket is now automatically connected to a constant, such that `getInputSocketReader` will never return a NULL pointer. This breaks the previous test method, which needs to be replaced by more explicit flags. Luckily this was done only for very few output nodes (Composite, Viewer, Output-File). These now use the regular SetValueOperation default in case "use alpha" is disabled, but set this to an explicit 1.0 value instead of mapping to the node socket.
Fix strict flags compilation error in box pack

No need to check q >= 0 in quad_flag() since q is
an unsigned int argument.
Revert previous change after discussion with Campbell

Let's just be really verbose and it some compiler gives
issues tell him NOT to do this.

We shouldn't really workaround compiles' idiocy..
Add message for constraint poll

Was confusing for Python devs when these fail silently
Fix T39843: cycles memory leak rendering with high transparent depth.
BoxPack: replace macros with functions

also correct error merging vertices
Fix T39895: Displaying the armature layers popup in edit mode always fails.

In fact, armature layers operators (set layers, and show all) were kind of messy and broken
in Edit mode (Select layers had two different operators for Pose and Edit modes, both
using the same funcs that could only work in Pose mode, Show All was supposed to be
used in both modes but again, its exec code could only work in Pose one).

Fixed that by:
* Using only one op for each task, for both modes (with adapted poll func).
* Replacing 'object from context' access by an helper that returns the right Armature
object in both Edit and Pose modes.
Always init pointcache frame step to 1.

Note it was already the case for many simulations (cloth, rigidbody, etc.), just doing this
systematically in BKE_ptcache_add() now, will avoid us some recurring bug reports.
Advanced users will know when they can/have to raise this parameter!
Fix for transform local-axis calculation with zero length normals
Outliner: avoid using bitshift when hashing (which could use negative numbers)
Fix T39896: lock view rotation, behavior not consistent
Avoid integer overflow in build_implicit_tree_helper
Cycles: avoid some CUDA performance on scenes without deformation motion blur.
Code cleanup: use 'const' for arrays (blenkernel)
Code cleanup: use 'const' for arrays (blenlib)