A note on libstdc++/6746

[Paolo Carlini]

Hi all,

today, while playing with something else I noticed what follows: if I 
revert the patch for libstdc++/3746 then libstdc++/6746 is OK. Also, if 
I apply to a stock 3.0.4 the fix for 3746, then 6746 appears there too.

Therefore, I reckon, 6746 is a very old latent bug, exposed by the patch 
for 3746: I didn't expect this!

I hope Benjamin (who is on it) will find this useful.

Ciao, Paolo.