Add support for non-volatile default conf files

[jberry@…]

It is useful to be able to install as part of a port certain files that will not be uninstalled or overwritten by subsequent installations or upgrades to the port.

This patch adds support for intallation at activation time of "default" files which will not be tracked as part of the installed port, and do not overwrite existing files of the same name.

The new option activate.copy_defaults accepts [multiple] pairs of src/dst file paths. At the tail of the activation phase, each src file is copied to its paired dst file iff dst doesn't already exist.

[jberry@…]

Patch to base/src/port1.0/portactivate.tcl