More libsodium stuff

[Hal Murray]

I'm mostly caught up again.

I have a hack that makes it work on NetBSD.
The problem is that the run time loader/linker doesn't look in /usr/pkg/lib where libsodium ends up.  I added a link from where it does look:
      ln -s  /usr/pkg/lib/libsodium.so.18 /usr/lib/libsodium.so.18

CentOS 6 needs something similar.

I added various notes to INSTALL   Please check.


I forgot to add that downloading the tarball for Debian Wheezy doesn't work because it doesn't have the right certificate.  I downloaded it on a newer system, then used scp.

-- 
These are my opinions.  I hate spam.