tests: avoid spurious failure in 'suffix3.tap' * tests/suffix3.tap (foo.zoo): This C++ file fails to compile with older g++ (3.4.4) on Cygwin 1.5.25 if we #include <iostream>. Don't do that, since it's not strictly required, and the "using namespace" directive is already enough to ensure the file contents is valid C++ but invalid C.