Revert "x/tools/container/intsets: remove unused function"

This reverts commit 79902b439b3ef4c163ff5e96ac1f282f31c8a131.

Reason for revert: build broken on some platforms.

Change-Id: I5ceddc305580ff97f47ae27da831f99e96dab424
Reviewed-on: https://go-review.googlesource.com/37539
Reviewed-by: David R. Jenni <david.r.jenni@gmail.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
1 file changed