Introduced two new methods:

powerOff():
This will put the enc28j60 module into the sleep mode.

powerOn():
This will wake up the enc28j60 module back from sleep mode.

Usage:

void loop()
{
  Ethernet.maintain();
  [...]
  Ethernet.getNetwork().powerOff();
}
allow only 2 inbound UDP-packets instead of configurable array saves another 150 bytes of flash
save another 26 bytes of flash by using uint8_t instead of uint16_t for 8-bit enc28j60 register
adjust define for NUM_MEMBLOCKS to match previous commit
auto-free block when udp-packet is read entirely
save another 658 bytes of flash by using all static access in network and mempool
Merge remote-tracking branch 'upstream/master'
add Enc28J60.powerOff(), Enc28J60.powerOn() and Enc28J60.getrev()
add Print::write to UIPClient
allow to define a timeout independent of uip for UIPClient::connect()
add ability to read link status to Enc28J60Ethernet.h
fix regression introduced in 4cf19395480a877df6f96b4ff1d0b17e47594c2d
cosmetics (debug output)
Merge branch 'checklink'
Merge remote-tracking branch 'upstream/master'