Update <netpacket/packet.h> for Linux 4.3.

Update <netpacket/packet.h> for Linux 4.3.

In the course of reviewing Linux 4.3 changes for any glibc header
updates needed, I found that
sysdeps/unix/sysv/linux/netpacket/packet.h was extremely out of date
(last updated for Linux 2.3.15, it seems).  This patch updates the
sets of constants present in that header to include those added to
those sets in newer kernels (include/uapi/linux/if_packet.h).

Tested for x86_64 (testsuite, and that installed shared libraries are
unchanged by the patch).

	* sysdeps/unix/sysv/linux/netpacket/packet.h (PACKET_COPY_THRESH):
	New macro.
	(PACKET_AUXDATA): Likewise.
	(PACKET_ORIGDEV): Likewise.
	(PACKET_VERSION): Likewise.
	(PACKET_HDRLEN): Likewise.
	(PACKET_RESERVE): Likewise.
	(PACKET_TX_RING): Likewise.
	(PACKET_LOSS): Likewise.
	(PACKET_VNET_HDR): Likewise.
	(PACKET_TX_TIMESTAMP): Likewise.
	(PACKET_TIMESTAMP): Likewise.
	(PACKET_FANOUT): Likewise.
	(PACKET_TX_HAS_OFF): Likewise.
	(PACKET_QDISC_BYPASS): Likewise.
	(PACKET_ROLLOVER_STATS): Likewise.
	(PACKET_FANOUT_DATA): Likewise.
	(PACKET_MR_UNICAST): Likewise.