MFstable/10 r291573:

MFC r278932:
r278932 (by pfg):

libc: clean some set-but-not-used errors.

These were found by gcc 5.0 on Dragonfly BSD, however I
made no attempt to silence the false positives.

Obtained from: DragonFly (cf515c3a6f3a8964ad592e524442bc628f8ed63b)