Do not compile unused functions in ccdensity

[TiborGY]

Description

ccdensity::resort_tei() appears to be completely unused, it is never called anywhere, it is not PSI_API and it is commented out from CMake as well as at the declaration site. This is because it is part of an incomplete project to implement frozen-core CC gradients. Comment added at the declaration site to inform future devs about its status.

There are also a bunch of functions which were only called by resort_tei(), or by functions only called from resort_tei(). They were enabled in CMake. Commented them out in CMake.

Todos

• Unused functions/files are no longer compiled in ccdensity: classify, distribute, file_build, idx_error and idx_permute

Status

• Ready for review
• Ready for merge

[lothian]

Actually, this code was (is?) part of an old effort to add frozen-core capabilities to the CC gradient code. I'd prefer to leave it in place for now until I can develop a plan to resurrect the work.

[TiborGY]

Actually, this code was (is?) part of an old effort to add frozen-core capabilities to the CC gradient code. I'd prefer to leave it in place for now until I can develop a plan to resurrect the work.

Fair enough. I have reverted the deletions, commented out the currently unused files in CMake instead, and added a comment above the declaration site pointing to this PR.
Just in case someone else gets the idea of removing it.

[JonathonMisiewicz]

Frozen core gradients are one of the items on my to-do list. (libtrans is of course the problem.) resort_tei may not be needed. I'll make a note to reach out to TDC when that happens. Maybe at PsiCon. 🙂