Turn off warning for unused imports when building base.
Turn off warning for unused imports when building base.

The import here is unused by design.  It's part of a pattern to get
GHCJS to move common code from codeworld-base into a separate
JavaScript file and speed up downloads.

Ye-Yong-Chi/codeworld,three/codeworld,stefan-j/codeworld,stefan-j/codeworld,tgdavies/codeworld,venkat24/codeworld,tgdavies/codeworld,google/codeworld,parvmor/codeworld,google/codeworld,alphalambda/codeworld,alphalambda/codeworld,google/codeworld,Ye-Yong-Chi/codeworld,xwysp/codeworld,venkat24/codeworld,parvmor/codeworld,nomeata/codeworld,pranjaltale16/codeworld,xwysp/codeworld,alphalambda/codeworld,nomeata/codeworld,pranjaltale16/codeworld,three/codeworld,three/codeworld,nomeata/codeworld,pranjaltale16/codeworld,Ye-Yong-Chi/codeworld,venkat24/codeworld,parvmor/codeworld,xwysp/codeworld,tgdavies/codeworld,stefan-j/codeworld