Log Message:
rc.d-boot: Fix for unprivileged users on Darwin

pkgsrc changes:
---------------
  * Replace hardcoded /etc with ${PKG_SYSCONFDIR} to find rc.d scripts installed
    by unprivileged users.
  * For unprivileged bootstrap, the INSTALL script copies
    org.pkgsrc.rc.d-boot.plist to $HOME directory of the user who installs the
    package. This avoids making assumptions on the unprivileged user during the
    build process.