The example of how to create a first target system, which is located
in the System Principles document, is now extended to also include an
example of code upgrade.

A new chapter is added to System Principles explaining different
issues when upgrade includes new versions applications within
Erlang/OTP.

This example module can now create and install a release in a
directory which contains unicode characters. The erlang node must be
started with the +fnu* switch for this work.

OTP-10106
OTP-10107

systool:make_tar stores the rel file in the releases directory. When
unpacking with release_handler:unpack_release, the file is
automatically moved to releases/<vsn>/. If, however, the tar file is
unpacked manually, the rel file might not be moved, and the next
release unpacked might overwrite the rel file. To overcome this,
systools:make_tar now stores a copy of the rel file in releases/<vsn>/
directly and it is not longer necessary to move the file after
unpacking.

The reason for keeping the file in the releases directory also is that
is needs to be extracted separately before the release version <vsn>
is known.

Commit 7ed11a886fc8fcaf3c2b8324294e2f24e02b0f28 removed the "-f" flag
from chmod calls in Makefiles:

| "-f" is a non-standard chmod option which at least SGI IRIX and HP UX
| do not support. As the only effect of the "-f" flag is to suppress
| warning messages, it can be safely omitted.

Meanwhile, new "chmod -f" calls have been added. This commit removes the
"-f" flag from those new calls.