Fix buid errors for PostgreSQL support

NetBSD does not install PostgreSQL headers in a postgresql directory but
it is not a common case. The previous commit removed this directory.

Add support for several BSD OS

Neither NetBSD nor FreeBSD implement reentrant functions of rand48
family (and probably neither OpenBSD nor DragonFlyBSD). This patch
replaces lrand48_r(3) by rand_r(3).

The goal is to isolate code modules more from each other and to have less
recompilation in case of changes in headers.

There was CRC32 code in the library, but it was only used at one place. So to
reduce the size of the common library code, I moved CRC32 to the point where it
is used.

Fixes for gcc 8.3.0

See merge request !2

This is present since C++11. No need anymore for switching between different
implementations.

I'm working on creating header files with a structure that matches the
individual code modules.

Make `pmalloc` internal so that users always have to call `pmalloco`.

Allows to remove some legacy IPv4 only code.

jabberd starts again now.

Compiled the code with a modern C++ compiler and fixed the warnings it
gave.

The compiled result is still not running. Different symbols are being
generated of jutil_delay, therefore dynamic linking on startup is not
working.

This commit makes the compile work on a current amd64 linux system.
However jabberd is not running again.

There is a problem that that symbols in the ELF tables don't completely
match. I still have to investigate into this.

Also there are a lot of compilter warning that have to do with changed
lengths of some times on a amd64 system, that I still have to fix.

This code wasn't updated and adapted to the other parts of the server.
So I don't think it will work anymore.

With this commit jabberd compiles again.

* Removed individual configurations for GnuTLS settings.
  (TODO: replace with gnutls_priority_set_direct(...))
* base jabberd executable compiles again.

Adding JSM configuration setting that will cause JSM to store presence information of all contact's of a user to xdb.