Blender Git Loki

Bugfix #26221

Two bugs in one:

- Lukas commit monday for new group/socket handling accidentally removed
to set socketype in stacks, which as used by (texture) nodes to detect
whether value, color or vector had to be read.
Result was that all texture nodes were rendering as B&W

- Old 2.5 bug: preview renders for texture nodes didn't call a
NodeEndExec function, which gave crashes on deleting nodes.

The change in interface_hanlers.c is only a comment to explain
how keymaps are being found.