Fix compiler warning in stuffvalue.c re: fabs(3).
Fix compiler warning in stuffvalue.c re: fabs(3).

Fixed by #including <math.h>

adfernandes/pcp,wuliming/pcp,wuliming/pcp,adfernandes/pcp,wuliming/pcp,adfernandes/pcp,adfernandes/pcp,wuliming/pcp,adfernandes/pcp,adfernandes/pcp,wuliming/pcp,wuliming/pcp,wuliming/pcp,adfernandes/pcp,adfernandes/pcp,wuliming/pcp