Reduce sa.log size

Currently we dump many interesting things. Unfortunately, on large applications this leads to huge files:

```bash
andrea@ruchill$ ll -h coreutils-6.10/obj-llvm/src/klee-last/sa.log 
-rw-rw-r-- 1 andrea andrea 3.4M Aug 14 09:23 coreutils-6.10/obj-llvm/src/klee-last/sa.log
```