This commit also adds a check to see that all files that
are part of an xi:include also have part of XML_FILES
and vice versa. It also fixes any applications where this
was not true.

Several people have requested that the assert macros in EUnit should be
moved out to a separate header file. This patch puts them in
stdlib/include/assert.hrl, which gets included by the eunit.hrl file.
Thus, nothing changes for eunit users, but the asserts can now also be
included separately.

* dgud/stdlib/rand/OTP-12586:
  stdlib: Document and add normal distributed random value function
  stdlib: Add new random functionality/module

It is needed in various tests. It uses the Ziggurat algorithm, which
is the fastest that I know.

Introduce erl_anno, an abstraction of the second element of tokens and
tuples in the abstract format. The convention that negative line
numbers can be used for silencing compiler warnings will no longer
work in OTP 19; instead the annotation 'generated' is to be used.

This module has been marked experimental for more than 15 years,
and has largely been superseded by the pg2 module from the kernel
application. The original pg also has no tests and has not been
updated in the last 15 years other than small maintenance edits
(like adding specs or replacing pid/1 by is_pid/1). It is pretty
unlikely that anyone uses it today and its presence is simply
confusing as people should be using pg2 anyway.