Add sanity check to "remove-deprecated-files" target.

Import helper awk script to detect objects linked to particular
library.

Separate the check to a new target "check-deprecated-files" in
etc/Mak

Add sanity check to "remove-deprecated-files" target.

Import helper awk script to detect objects linked to particular
library.

Separate the check to a new target "check-deprecated-files" in
etc/Makefile and utilize the script to report libraries that are
still in use.

Default is to check directories under /usr/local/. Additional places
to search may be specified via CHECK_DEPRECATED_DIRS variable, like:

make CHECK_DEPRECATED_DIRS="/opt/lib /opt/bin" upgrade

Suggested and reviewed by: Sascha Wildner

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