PKGNAME if we are installing to an alternative location so that the
pkg system doesn't complain about conflicts.
Now it is possible to install a gcc3 tree to some location where
it can be used to bootstrap another instance of itself...
-USE_NEW_TEXINFO, saves some patches
-symlink libiberty.a into build tree instead of buildlink/lib,
saves some patches
-put common make rules into Makefile.common (for all) and
buildaddon.mk (for all but the base "c" pkg)