Previously, unique identifiers for sockets were created automatically,
sometimes using .001 and sometimes _001. Now they are created
manually with the second format, but some files were saved with .001
format. I think this was only an issue in the vector math node.

rBd845ba481c6d fixed this problem in 3.1, but in a more general way.
After I merge this patch to 3.1, I will revert it, since the versioning
added in that commit will make this redundant.