implement a more lightweight version of fluids on top of this basic
mechanism. */
-extern long scm_tc16_fluid;
+extern scm_bits_t scm_tc16_fluid;
#define SCM_FLUIDP(x) (!SCM_IMP (x) && (SCM_CELL_TYPE (x) == scm_tc16_fluid))
#define SCM_FLUID_NUM(x) (SCM_CELL_WORD_1 (x))