Add kernel module and a simple configure tool to generate packets at full speed

Add kernel module and a simple configure tool to generate packets at full speed

Sending host:
  Athlon64 X2 3600+
  em(4) (1000PT), hw.em0.int_throttle_ceil set to 4000
  Result of a 10 seconds test:
  cnt 14475256, err 0, time 9.990372

Receiving host:
  Turion64 X2 TL-58
  msk(4) (Yukon EU), hw.mskc0.intr_rate set to 4000
  Output of 'netstat -w 1 -I msk0':
            input         (msk0)           output
   packets  errs      bytes    packets  errs      bytes colls
         0     0          0          0     0          0     0
         0     0          0          0     0          0     0
    103556     0    6213360          0     0          0     0
   1465259     0   87915540          0     0          0     0
   1461728     0   87703680          0     0          0     0
   1463788     0   87827280          0     0          0     0
   1456630     0   87397800          0     0          0     0
   1459206     0   87552360          0     0          0     0
   1464240     0   87854400          0     0          0     0
   1468240     0   88094400          0     0          0     0
   1464305     0   87858300          0     0          0     0
   1468011     0   88080660          0     0          0     0
   1200293     0   72017580          0     0          0     0
         0     0          0          0     0          0     0