Remember/restore ALLOCA_FOR_VAR_P over tuples

[Eric Botcazou]

> r172516, for reference also below.  I later saw that my patch causes
> cxg2001 to fail.  I've analyzed it enough to be sure that it's only
> exposed by this patch (due to inlining now happening), in fact it's a
> problem in IRA that is reproducible with a C++ testcase even without the
> patch.  I've filed PR48633 for this.

Thanks for debugging the problem.  I was expecting some fallouts in Ada because 
this will shake a little the compiler, but the results of our internal testing 
don't show other problems than this ACATS failure, so that's great.

-- 
Eric Botcazou