Due to my recent discovery of the problem with wcscoll in the
ru_RU.KOI8-R locale, I found that the gnulib regex module still
depended on the wcscoll module, even though it had been fixed not to
use the wcscoll function.  I fixed that (I thought) in gnulib.  Then I
removed a no-longer-needed explicit dependency in grep on the wcscoll
module.  Surprise!  That latter change broke several grep tests.
Tracking it down, I found that there was one more remaining dependency
from gnulib's regex module on wcscoll: via a use of HAVE_WCSCOLL,
which was no longer defined, once I'd removed the module dependency.

Bottom line: I removed that now-stale use of HAVE_WCSCOLL from
gnulib's regex_internal.h, and then, (with an update-to-latest gnulib)
removing the explicit module dependency from grep goes without a
hitch.