localedef: add newlines to error messages

These won't be added elsewhere, so add a little bit of room to make
these messages a little easier to read. The existing set is a mixed
bag, there are somewhere in the ballpark of 45, 46 printfs to stderr and
19 of those had newlines.

Reviewed by: yuripv
Approved by: re (kib)
Sponsored by: Klara, Inc.

(cherry picked from commit 3141e51d2e38fa7b9e6d81477dfa860d087c514d)
(cherry picked from commit dc8ee27074d4060549c6ecdc88eeec386691b479)