In the standard library in Rust before 1.2.0, BinaryHeap is not panic-safe

In the standard library in Rust before 1.2.0, BinaryHeap is not panic-safe. The binary heap is left in an inconsistent state when the comparison of generic elements inside sift_up or sift_down_range panics. This bug leads to a drop of zeroed memory as an arbitrary type, which can result in a memory safety violation.