[v3] debug mode

[Rainer Orth]

Benjamin Kosnik writes:

> alright dudes, try the attached.
> 
> tested x86/linux
> tested x86/linux -D_GLIBCXX_DEBUG

thanks, this fixes the compile failure and bootstrap completes.  However, a
couple of execution failures now come up during the testsuite run:

9215:./g++-dg-compat-eh-nrv1-01: /sbin/loader: Error: Unresolved symbol in /amnt/figaro/volumes/obj-gcc/gcc/obj.alpha/gcc-3.4-20031120/4.0f-gcc/alpha-dec-osf4.0f//libstdc++-v3/src/.libs/libstdc++.so.6: _ZNK11__gnu_debug16_Error_formatter14_M_format_wordImEEvPciPKcT_
9215:./g++-dg-compat-eh-nrv1-01: /sbin/loader: Fatal Error: this executable
has unresolvable symbols

	Rainer