update for ports/www/mozilla-firebird

[Trevor Johnson]

- update to 0.8
- new name "firefox"
- make PLIST from a fake installation
- restore original credit in Makefile
- optionally install headers and share/idl (addresses PR 62631, submitted by
  Palle Girgensohn)
- start to use Perl instead of REINPLACE_CMD, since we need Perl anyway
- tell users about the build options

<URL:http://people.freebsd.org/~trevor/ports/firefox-skeleton-0.8.tar.bz2>
-- 
Trevor Johnson