modified:   examples/udp_echo_server/udp_echo_server.c

Fixed bug, the buffer was not echo'ed as supposed too. An empty buffer was send, instead of the received message
modified:   src/libdpdkif/dpdkif_user.c

Modifications made to make dpdkif_user work with the vmxnet3 driver:
-No support for TX Multisegments
-No support for TX Offload
-The vmxnet3 needs at least 512 TX descriptors and recommends at least 256 RX descriptor
-The amount of mbufs in the defined rx&tx pools should contain equal amount of rx or tx descriptors + a certain amount extra to cope with packets bursts
Merge pull request #11 from ywahl/master
Tweaks to make udp_echo_server easier to test:

  - By default, use DHCP.
  - Bind server to any address.
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