[libstdc++] fix (tricksy, wicked, false) sizeof bug in vterminate.cc

[Gabriel Dos Reis]

Phil Edwards <phil@jaj.com> writes:

| Is not so good when used like this:
| 
|     char* dem = __cxa_demangle(name, 0, 0, &status);
| 
|     writestr("terminate called after throwing an instance of '");
|     if (status == 0)
|         writestr(dem);

Scary.

Thanks,

-- Gaby