Wiki page about synchronizing kernel and userspace headers

[Allan McRae]

I have added a wiki page about synchronizing headers between Linux and
Glibc based on the work done earlier in the year on the net headers.

https://sourceware.org/glibc/wiki/Synchronizing_Headers

The process actually looks fairly straight forward now the ground work
has been done, so hopefully it is clear.

I added the two header that were discussed on the list recently as a
note at the end, but will add them to the bug tracker with a keyword and
just provide the link there at some stage.

Cheers,
Allan