istype is invokish and its return value ought to be INT, not VOID

so i just comment it out for the time being.
support for bindpos_i is trivial to add
add isint/isnum/isstr/islist/ishash

in the interest of finding out what other ops will cause
bails down the road. These ops ought to be implemented
by generating a tiny bit of assembly code instead of a
C call, but i leave that for brrt++ to do.