I installed libstdc++-2.95.3-0.20000517. It doesn't include the backward-compatibility library libstdc++-libc6.1-2.so.3 for x86, although there's code in the spec file which seems to try to install it (at least for sparc). It should be included for x86 too. I was able to install this upgrade even though groff-1.15-9 requires libstdc++-libc6.1-2.so.3. I do not understand why I was allowed to install this upgrade; shouldn't rpm have informed me that the upgrade would erase a library which another installed package depends upon?
assign to jakub
This has been fixed since then, there are compat-libstdc++ and libstdc++ as separated packages