[exim] CAVEAT: Exim Specification chapter numbers moved

Folks,

For the first time in a while, with the release of 4.80 the Exim
Specification has gained new chapters somewhere other than at the end of
the document. This is because we added two new authentication drivers,
so those of course had to go in with the other authentication drivers.

Thus various chapter numbers have changed. (Normally, this only happens
to the three Index chapters, and those are not thrilling reading which
folk get pointed at often).

I mention this in case anyone providing help or support for their users,
or here on exim-users, has templated responses which reference the Spec
by chapter numbers.

Chapters 38 and 39 are new, covering gsasl and heimdal_gssapi
respectively.