Make variables unsigned to avoid ub in calculation
Make variables unsigned to avoid ub in calculation

According to ubsan we get several times into undefined behaviour due to signed overflow:
foreign.c:91:21: runtime error: signed integer overflow: 3291370622602663862 * 3 cannot be represented in type 'long int'

This happens only when the symbol name is relatively large like as for the call:
symhash (s=0x5555558caab8 "(cs)set_enable_object_backreferences")
mflatt/ChezScheme,mflatt/ChezScheme,mflatt/ChezScheme