[Ada] Bootstrapping mainline GNAT fails

[Robert Dewar]

<<Read the message carefully: 3.14p works fine.  What don't work are some
kludged-up compilers that try to use GC 2.95 or GCC 3.0 sources.
>>

The compilers that tried to use 2.95 and 3.0 were badly broken, and fail
on many, perhaps most, large applications, so it is not at all surprising
that they fail on the compiler, and it is technically infeasible to work
around these bugs.