[PATCH] ignore -mconstructor-aliases when adding field paddings for asan

[Kostya Serebryany]

We need to emit the actual DTOR instead of replacing it with the base class DTOR, because later in clang codegen this DTOR will be instrumented with __asan_unpoison_intra_object_redzone and its body will become non-empty

http://reviews.llvm.org/D6038