* When installing a binary package, export the file name of the package

* When installing a binary package, export the file name of the package
  as PORTAGE_BINPKG_FILE in order to give bashrc users an opportunity
  to do various things such as remove binary packages after they're
  installed.

* Add a note in ebuild.sh explaining why hardcoded bash lists are
  needed for backward compatibility with <portage-2.1.4 since they
  assume that a newly installed version of ebuild.sh will work for
  pkg_postinst, pkg_prerm, and pkg_postrm when portage is upgrading
  itself.

svn path=/main/trunk/; revision=8878