Blender Git Loki

UI: region overlap now works for headers as well.

This is for the 3D viewport and image editor. A remaining issue is
that pulldown menu buttons only show text, which is not visible on
all background colors, so making the header entirely transparent
does not work well at the moment.

Merge branch 'blender2.8' into greasepencil-object

Cleanup: Remove unused and change comments

Edit-mesh: multi-object reveal

Edit-mesh: multi-object hide

Edit-mesh: multi-object delete edge loops

Color PIcker use list of materials not object materials

Now, the list shows all grease pencil materials and not only the materials of the active object.

If the material selected is not in the active object material slots, the material is added automatically when draw.

Fix crash with select linked when nothing is under the cursor

There is no object to update anyways, and there is no valid basact when the
nified_findnearest() test fails.

How to reproduce the bug: Try to select linked (L) with selected faces but
withotu mouse hovering any mesh.

Bug introduced on: rBbfc9d426bb95 (original multi-object edit commit).

Edit-mesh: multi-object select less

Edit-mesh: multi-object select more

Fix missing show_weight from overlay UI

Missed when moving settings out of the mesh.

Cleanup: Rename function

Cleanup: Remove unused parameter

Show the 3D cursor by default

Was committed as part of unrelated change: D3198.

Add new modifier callbacks for switching from DerivedMesh.

Fix extrude glitch where undo state was visible

Merge branch 'blender2.8' into hair_guides

Cleanup: Remove unused variable

Use Brush material for Fill brush

Now the color used is the assigned to the brush and not the active color in material slots.

Fix compiler errors after merge