different gccs

[Bob Lockie]

This is based on behavoir/assumptions.

I think libsupc++ is included in gcc-2x but not in gcc-3x.

I need libstdc++ in gcc-2x but I need both libstdc++ and libsupc++ in 
gcc-3x but libsupc++ does not exist in gcc-2x.

AC_CHECK_LIB( stdc++, main, , AC_MSG_ERROR( [*** stdc++ library is 
required ***] ), )

AC_CHECK_LIB( supc++, main, , AC_MSG_ERROR( [*** supc++ library is 
required ***] ), )

Are my assumptions correct and how can I write a configure.in that works 
regardless off gcc version?