Add 802.1Q ethertypes used in the wild

[donner]

Summary

Older network equipment used the ethertypes 9100, 9200, and 9300
for outer VLANs, before standardization introduced 88a8.

Test Plan

Validate, that the definition is in sync with other definitions.

Excerpt from contrib/tcpdump/ethertype.h

#ifndef ETHERTYPE_8021Q
#define ETHERTYPE_8021Q         0x8100
#endif

/* see:
        http://en.wikipedia.org/wiki/IEEE_802.1Q
    and http://en.wikipedia.org/wiki/QinQ
*/
#ifndef ETHERTYPE_8021Q9100
#define ETHERTYPE_8021Q9100     0x9100
#endif
#ifndef ETHERTYPE_8021Q9200
#define ETHERTYPE_8021Q9200     0x9200
#endif
#ifndef ETHERTYPE_8021QinQ
#define ETHERTYPE_8021QinQ      0x88a8
#endif

[philip]

Looks good to me. I'll commit this.