Bootstrap broken at the beginning of libstdc++-v3

[Vladimir A. Merzliakov]

> Hi,
> 
> current mainline doesn't bootstrap on at least i686-pc-linux-gnu and 
> x86_64-unknown-linux-gnu.
> 
[skip]
> appending configuration tag "CXX" to libtool
> checking for exception model to use... configure: error: unable to 
> detect exception model
> make[1]: *** [configure-target-libstdc++-v3] Error 1
> make[1]: Leaving directory `/home/paolo/Gcc/cvs-dirs/gcc-head-build'
> make: *** [bootstrap] Error 2
> 
Same error at i386-unknown-freebsd5.1

Vladimir