[RFA] fix disassemble foo::bar::~bar

[Tom Tromey]

>>>>> "Keith" == Keith Seitz <keiths@redhat.com> writes:

Keith> (gdb) p foo::~bar
Keith> name of destructor must equal name of class

Keith> How much more useful is that than

Keith> (gdb) p foo::~bar
Keith> There is no field named ~bar

I think the difference is that with the current code, it is a parse-time
error, but if we remove destructor_name_p, then it is an evaluation-time
error.  This difference matters for breakpoint conditions.

Searching the type's function fields seems like the very best, to me.
I couldn't think of a drawback of this anyhow.

Tom