Enable -n command line option for non-Windows Squid builds

Enable -n command line option for non-Windows Squid builds

This command line option is used on Windows to name the service instance
of Squid being run and/or managed. At this point it still only has
useful effect on Windows, but can now be used by components on other
systems as well.

Show the running instance service name in cacehmgr and -v output.

Also remove _WIN_SQUID_DEFAULT_SERVICE_NAME macro which duplicated the
APP_SHORTNAME macro. This changes the Windows service name from Squid to
squid (lower case) on future Squid-3 for Windows.