Use-after-dtor detection for trivial base classes.

-fsanitize-memory-use-after-dtor detects memory access after a
subobject is destroyed but its memory is not yet deallocated.
This is done by poisoning each object memory near the end of its destructor.

Subobjects (members and base classes) do this in their respective
destructors, and the parent class does the same for its members with
trivial destructors.

Inexplicably, base classes with trivial destructors are not handled at
all. This change fixes this oversight by adding the base class poisoning logic
to the parent class destructor.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D119300