belongs here still, but this came up often, it avoids having to
switch tabs a lot when creating things.
Also renamed uiLayoutFreeBlock to uiLayoutAbsoluteBlock.
#19345: can't get out of grayed out pointer field.
#19342: item_pointerR fields can't be cleared with one item.
#19341: fix hanging tooltips when manipulating regions.
#19339: context panel still allowed tabbing, but it has no header.
#19334: editing SSS settings crashed previewrender.
#19330: object mode could not be switched on from the header menu.
Added SpaceLogic, to restore the old logic buttons into.
In future it can be used for a more advanced logic editor, with
states, behaviour, whatever. We'll see!
This commit only adds the backend for new space. Committed this
now as reference for when we need another space type. It's still
not well plugin-able (dynamic space types), but my idea is to just
have a new SpacePlugIn for this, with a neat small API to define
all relevant callbacks.
Also note the icon for the spacetype is wrong still.
