Backporting to 4_0 the latest friend bits

[Paolo Carlini]

Hi Mark,

> I agree; that's why I asked to see the patches.

Humm, maybe a couple of links are in order, for your convenience:

    http://gcc.gnu.org/ml/gcc-cvs/2005-03/msg00681.html
    http://gcc.gnu.org/ml/gcc-cvs/2005-03/msg00679.html

(I understand that Kriang volunteered to regtest and, if necessary (most
likely not) tweak the patches for actual 4.0 inclusion)

Paolo.