refs is now an INT32 again.

Rev: src/array.h:1.24
Rev: src/constants.h:1.13
Rev: src/gc.h:1.59
Rev: src/interpret.h:1.63
Rev: src/mapping.h:1.30
Rev: src/multiset.h:1.15
Rev: src/object.h:1.52
Rev: src/pike_types.h:1.41
Rev: src/program.h:1.99
Rev: src/stralloc.h:1.48