cxxabichk is currently tuned to minimize output. In particular, it won't
complain about functions in vtable which is can't resolve to a name. Set
LIBCHK_DEBUG=0 to see these.

/*
 * Maintainers can get additional detail by setting the environment variable
 * LIBCHK_DEBUG to these values
 */

   #define LIBCHK_DEBUG_NEWVERS            0x0001
   #define LIBCHK_DEBUG_OLDVERS            0x0002
   #define LIBCHK_DEBUG_CLASSDETAILS       0x0004
   #define LIBCHK_DEBUG_CXXHUSH            0x0008


