fix malloc_allocator, rfc c++ front end bug?

[Paolo Carlini]

Richard Henderson wrote:

>I have absolutely no idea why this isn't failing IN THE TESTSUITE for
>i686-linux.  If I preprocess the test case on i686 and then run the .i
>file through the compiler, I do get these same errors.  I can only imagine
>that it's a bug in the front end somehow, but I don't have a clue how
>to go about showing that.
>  
>
Maybe precompiled headers related? If available, are used when running the
testsuite and you don't notice if an include is missing... Therefore 
everything
goes as-if precompiled headers were *not* available on alpha-linux. Is 
my guess
correct?

Of course your fix is ok, but let's make sure we understand what's going on!

Paolo.