Our Ada 95 front end has a compile-time option which will
cause it to produce extra warnings on any usages which might
be upward compatibility problems.  However, I'm not sure
it is worth it.  The problems that are truly due to a
language change are few and far between and usually very
easy to fix.  The real problems tend to be implementation-specific
packages, pragmas, or attributes which aren't supported by
the new compiler (the fact that it is Ada 95 rather than
Ada 83 is almost irrelevant).

-Tucker Taft