More libtool madness: Every package which was using c++ and libtool fixup

More libtool madness: Every package which was using c++ and libtool fixup
was linked against libstd++ even though if it should have been linked
against uclibc++. This is fixed by providing a special version of libtool
fixup for packages which should use uclibc++. Not pretty but functional.
Packages linking against uclibc++ should use PKG_FIXUP:=libtool-ucxx instead of
PKG_FIXUP:=libtool

Somebody should probably check all packages using c++ with a dependency on stdlibc++
if uclibc++ can be used instead now.

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@16317 3c298f89-4303-0410-b956-a3cf2f4a3e73