Change docs to note posfix totally broken more than two releases ago/ no ETA

[hcoin]

The pfsense docs have this regarding the postfix package:  https://doc.pfsense.org/index.php/Postfix
Reading the forums you'll note many think of this package as the thing that puts pfsense 'over the top' to be the system of choice.

However, this package has been broken to the extent that no combination of pfsense config options will allow it to start.

And, this breakage has existed for several releases now, with no sign I could find (after some considerable looking)  there's any fix to be expected, much less a projection as to when.

This breakage has caused all who integrated postfix as a integral part of their overall system to not upgrade pfsense for quite some time.  It's not so easy to change email setups, no matter the value of further pfsense releases.

So I suggest the documentation to be updated for this package, near the top, as follows:

*The last version of pfsense supporting this package is version 2.1.5. Later pf versions will cause this package not to start.  It is not known when or if a new version will be available.  Do not install this package if you expect it to 'just work'.

[hcoin]

P.S. I suggest also putting a 'broken since 2.1.5' on the 'packages' pfsense page.  It will save many hours of avoidable frustration and avoidable ill will generation since presently the user is given to think the reason it won't start is 'down to' the user's poor configuration choices, even though no combination could work.