C++ demangler horrors

[DJ Delorie]

> 2) when libiberty is configured for the target, do *not* test for a
>    C++ compiler.  Instead, get configure-target-libiberty to depend on
>    configure-target-libstdc++-v3 (does this introduce any cycles?),

This doesn't work when libiberty is built for one of the projects
other than gcc - like binutils or gdb - which doesn't have libstdc++v3
in it.

Or, at least, you won't always get the results you expect.