[patch] fix exp/12117

[Tom Tromey]

>>>>> "Doug" == Doug Evans <dje@google.com> writes:

Doug> a) it seems like it's not just c/v, e.g., it's also the address space
Doug> [and perhaps here's a case where there are more bugs in this area :-)]

Yeah.  Actually, this one seems like it could cause real problems
somewhere.

Doug> b) it seems odd to have to build such types on the fly
Doug> [I can imagine a proliferation of such objects that aren't attached to
Doug> anything concrete in the debug info, and just cause confusion]

I'm not sure I understand.  The qualified variants are all linked
together and allocated alongside the main_type, so we don't have to
worry about memory leaks or excess type reinstantiation.  In fact I
think the user can cause this sort of type allocation by writing "const
sometype" in an expression.

Tom