You're trying to compile the module with a different C compiler than your perl binary was made with (or at least the one it thinks it's configured to use). Check that you haven't upgraded to a newer C compiler (or upgraded to a newer binary perl and not a suitable similar vintage cc), or that someone's changed your PATH and you're picking it up from somewhere else. Also wouldn't hurt to give a bit more information like what OS this is on (I'm guessing Linux by the -DDEBIAN, but more specifics might be useful).

Addendum: And if none of that makes sense, it's time to go prostrate yourself before your local sysadmin or C guru and see if they can't get things straightened out.