Add tests for the cpp version

[jvoisin]

• new/delete
• new[]/delete[]
• size mismatch on delete
• std::bad_alloc on invalid new
• no exception if configured this way on invalid new
• …

[struct]

Did you try running make cpp_tests ?

[jvoisin]

Yes, but they only check that things are ~working, but not that isoalloc is catching bad things™