patch that caused regression PR c++/8906

[Janis Johnson]

The mainline regression reported in PR c++/8906 showed up starting with
this patch, which might merely uncover an existing problem:

>2002-07-10  Jason Merrill  <jason@redhat.com>
>
>	PR c++/6255
>	* decl.c (lookup_name_real): Build a new TYPENAME_TYPE rather than
>	modifying the old one.

Here's a small test case that causes the ICE, which occurs in the
mainline, the 3.2 branch, 3.2.1, 3.2, and 3.1.1, but not 3.1:

---------------
template <class T> class CO {
  class CI1 {
    class CI2;
  };
};

template <class T> class CO<T>::CI1::CI2 {}; 
---------------

Output from the compiler (from 2002-07-09 sources):

/home/janis/gnu/src/gcc-obj-tmp/gcc/cc1plus -quiet 8906.C
8906.C:7: internal compiler error: internal error: Segmentation fault
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://www.gnu.org/software/gcc/bugs.html> for instructions.

This information will also be added to the PR.

Janis