rrdupd.c: Use appropriate types for values
rrdupd.c: Use appropriate types for values

Now we use
- unsigned long for CPU ticks, to reduce overflowing
- unsigned long for Memory Usage, to support more than 4 GB of one type
  of usage
- float for CPU usage fraction, as double might be overkill

aandergr/serverstat-linux,aandergr/serverstat-linux,aandergr/serverstat-linux