Move everything to where it should be.
Along the way, we lose <net/ethertypes.h>. glibc only has a handful of these
types, and they're all in <net/ethernet.h>, not <net/ethertypes.h>. I've taken
the liberty of not including the AppleTalk ones, since it is 2016.
Also, <net/if_ether.h> should be <netinet/if_ether.h> (though with different
contents).
Bug: http://b/28519060
Change-Id: Ia41c3fc136fd3e6b008c8d08018e0629134ea6fc
Previously it couldn't be included alone. Also add a header and include guard,
and fix its siblings' include guards.
Bug: https://code.google.com/p/android/issues/detail?id=82638
Change-Id: I32139a4bda0a6b015508a2319bf4e1a1453345f2