remove a bunch of dangerous casts (useless casts from void * to something

remove a bunch of dangerous casts (useless casts from void * to something
else, in some cases by adding extra temporary variables.
IMO, it's much better practice to do

void *a;
int *p = a;
*p = 42;

rather than
void *a;
*(int *)a = 42;

okay miod@... to be revisited for some possible const additions later.