Make -Wdelete-non-virtual-dtor warn on explicit `a->~A()` dtor calls too.

-Wdelete-non-virtual-dtor warns if A is a type with virtual functions but
without virtual dtor has its constructor called via `delete a`. This makes the
warning also fire if the dtor is called via `a->~A()`. This would've found a
security bug in Chromium at compile time. Fixes PR26137.

To fix the warning, add a virtual destructor, make the class final, or remove
its other virtual methods.  If you want to silence the warning, there's also
a fixit that shows how:

test.cc:12:3: warning: destructor called on 'B' ... [-Wdelete-non-virtual-dtor]
  b->~B();
  ^
test.cc:12:6: note: qualify call to silence this warning
  b->~B();
     ^
     B::

http://reviews.llvm.org/D16206

llvm-svn: 257939