utils: Suppress an implicit declaration error
utils: Suppress an implicit declaration error

Signed-off-by: Hiroshi Hatake <54b742842f0d940c9715551f77be1b560ea6cc67@gmail.com>

tarcieri/cool.io,cosmo0920/cool.io,tarcieri/cool.io,tarcieri/cool.io,cosmo0920/cool.io