et analyses trace messages, and since trace message with timestamps
still always are based on erlang:now/0, we must keep the calls to
erlang:now/0 but suppress the warnings.

Most dependencies introduced are exactly the dependencies to other
applications found by xref. That is, there might be real dependencies
missing. There might also be pure debug dependencies listed that
probably should be removed. Each application has to be manually
inspected in order to ensure that all real dependencies are listed.

All dependencies introduced are to application versions used in
OTP 17.0. This since the previously used version scheme wasn't
designed for this, and in order to minimize the work of introducing
the dependencies.

As discussed in issue #240 *all* OTP library applications use the '.*'
wildcard as up and down version. This makes library applications
always up- and downgradeable. Using the wildcard version obsoletes
all maintenance tasks regarding library applications' appup files.
Additionally, it prevents upgrade problems caused by automatically
included application dependencies when using reltool to create
releases. Missing copyright headers are now consistently present.