Add UDP_GRO from Linux 5.0 to netinet/udp.h

[Gabriel F. T. Gomes]

On Thu, Mar 21 2019, Joseph Myers wrote:
> This patch adds the new constant UDP_GRO from Linux 5.0 to glibc.

Looks good to me.

$ git show v4.20:include/uapi/linux/udp.h | grep -E "UDP_GRO"
$ git show v5.0:include/uapi/linux/udp.h | grep -E "UDP_GRO"
#define UDP_GRO		104	/* This socket can receive UDP GRO packets */

> +#define UDP_GRO		104	/* This socket can receive UDP GRO packets.  */

OK.