Another HP-UX IA64 Build patch

[DJ Delorie]

> The problem here is that libiberty.h declares basename always, even if
> you aren't using it.

No, I'm proposing that we do NOT declare basename if the application
didn't run the HAVE_DECL test.  However, to prevent applications from
using basename() without the HAVE_DECL test (the char * return
problem), we then add a #define to effectively poison it.

Thus, we need the HAVE_DECL test if we use basename(), but if we don't
use basename() we don't need the HAVE_DECL test.