Disabling COMPAT_FREEBSD4/5/6/7/9 as a default kernel option

[voidanix at 420blaze.it]

Hello,
I wanted to discuss about bug 231768 a bit: it is about keeping 
COMPAT_FREEBSD4/5/6/7/9 on by default in the kernel configs.

The patch attached for the bug is for disabling these options by 
default, following a few reasons which I'm going to list here:
     - Keeping support for deprecated libraries isn't exactly the best we 
could do to avoid security issues (if there are any) as I'm sure nobody 
wants to spend that much time maintaining such stuff (it's enough to 
think about misc/compat4x in the ports tree: that version of FreeBSD was 
released on March 2000 and keeping 19 years old libraries around isn't 
ideal)
     - Devs should get track of time and realize that developing software 
using unsupported libraries is NOT something that you should do
     - Only a tiny fraction of the ports need COMPAT_FREEBSD9 or older: 
if the software won't compile without the legacy components (and has a 
replacement of some kind), considering removal wouldn't be a bad idea
     - This is on by default: most users don't care or don't use binaries 
that old

I don't see any practical reason to keep these options on by default, 
but I do appreciate any sort of input regarding this issue.

- voidanix