remove zpipe (a testing tool) from --enable-diagtools

This tool is no longer maintained and currently not used inside the
testbench. We keep it in the source tree for the time being in case that
it may be used in the future.
bugfix rsgtutil: deletion of logs at end of file was not reported

The verification function in rsgtutil tool did not report deletion of
whole signed blocks of lines from the end of the log file.
maintain ChangeLog