Blender Git Loki

Depsgraph: Switch away form string to const char* for node names

There is no real reason to have nodes storing heap-allocated name
and description. Doing this increases amount of allocations during
dependency graph building, which usually means somewhat slowness.

We're temporarily loosing some eyecandy in the graphviz visualizer,
but those we can bring back as a part of graphiz dump (which happens
much less often than depsgraph build).

This will happen in multiple commits for the ease of bisect in the
future just in case this causes any regression. This commit contains
ID creation API changes.