32 bits workaround

If you're interested, I wrote a quick and dirty workaround to let ZMap compile and work on 32 bit systems,
AFAIK, possible issues should be introduced only on the summary print (ignoring the couple of bytes of memory now
overallocated on 64bits).

Please ignore first commit, it was just an attempt to get ZMap to compile (and I had not realized yet the point of the lsh to generate the whole 2^32 IPv4 number).

Just noted I put "long long" and "unsigned long long" in different functions, but, for the purpose, they're pretty interchangeable.

Kudos for the very good work.