Same here, until some day clamav stopped working because the databases the update mirrors supplied where in a different layout, which resulted in everyone needed to update theire clamav core files. Whet i mean to say with this is that stuff can work for years and suddenly stop working..
Besides the fact that the installer should work, it's also very much suggested you start using ispconfig3 .. i've been running 2 for a long time and didn't want to switch, but i've migrated a few servers now and i can say i'm never going back to ispconfig2 .. with 3 i have way more control over what software i'm running (at least for me it's way cleaner then 2) ..
oke, all things aside, the installer can't find libstdc that's a fact, when the compiler is called with -lstdc++ it will start looking for the lib files it needs in the most common locations like /usr/lib/, /lib or /usr/local/lib .. if it can't find them you'll see the error you get. It's possible that those files are in a different location and you need to specify where those files are so the compiler can find them.
For libs you can use: LDFLAGS=-L<dir> ./configure ... <etc>
For header files (includes): CFLAGS=-I<dir>
So ehm, check and see if you have a file called libstdc++.so.* somehwere in:
/usr/lib, /lib or /usr/local/lib