etc/Makefile cleanup

[Matthias Schmidt <matthias@xxxxxxxxxxxxxxxx>]

Heho,

I cleaned up etc/Makefile a bit.  I removed almost all lines containing
"rm -rf $file" statements and moved the filenames to a new file called
src/FilesToRemove.Inc.  This file is included by etc/Makefile and used
to remove obsolete files.  New obsolete files can be added to that file
without polluting etc/Makefile.

I also added a short message and a 5 seconds delay to make really sure
that the user performed a "make installworld" first.  The message and
the delay could be removed if somebody argues.

http://leaf.dragonflybsd.org/~matthias/etc_makefile_update.diff

In-collab-with:  swildner@

If nobody objects, I'm going to commit the patch in a few days.

	Matthias