bug#31853: (27.0.50; binding case-fold-search is slow when there are many buffers)

[Aaron Jensen]

This is apparently the second time I've spent time tracking down perf
issues that have led to this same issue:

https://debbugs.gnu.org/cgi/bugreport.cgi?bug=23928

Is it possible to improve this somehow? In this instance it's actually
org-mode that's binding case-fold-search in a tight loop in
org-scan-tags.

Thanks,

Aaron