this is adapted from the RTAI math library and massaged to compile
only with rtapi_math.h includes

# EXTRA_CFLAGS += -I/usr/include -ffast-math -mhard-float \
# 	$(KERNEL_MATH_CFLAGS) \
# 	-D_IEEE_LIBM \
# 	-D_ISOC99_SOURCE \
# 	-D_SVID_SOURCE \
# 	-I$(BASEPWD)