pfring: improve error reporting at device opening

This patch improves the error message displayed if pfring_open fails.
util-ioctl: minor code cleaning.

Fix author e-mail and simplify an indentation.
util-ioctl: add GRO/LRO detection capabilities

This patch adds a new function GetIfaceOffloading which return 0
if LRO and GRO are not set on a interface and 1 if not the case.
af-packet: add warning message if LRO or GRO are set

This patch query the network interface to detect if LRO or GRO are
used in mmap TPACKET_V2 mode.
pcap: add warning about GRO and LRO usage

Use the new GetIfaceOffloading function to display a warning message
if pcap capture is used on Linux with GRO or LRO activated. This is
helpful for kernel after 2.6.31 were pcap will use mmaped capture.
TPACKET_V2 is used and this limit the size of the packet resulting
in truncated packets when merged packets are received.
util-ioctl: ioctl error should be a warning