clippy 0.0.208

A bunch of helpful lints to avoid common pitfalls in Rust
error: `0 as *const _` detected. Consider using `ptr::null()`
 --> $DIR/zero_ptr.rs:6:13
  |
6 |     let x = 0 as *const usize;
  |             ^^^^^^^^^^^^^^^^^
  |
  = note: `-D zero-ptr` implied by `-D warnings`

error: `0 as *mut _` detected. Consider using `ptr::null_mut()`
 --> $DIR/zero_ptr.rs:7:13
  |
7 |     let y = 0 as *mut f64;
  |             ^^^^^^^^^^^^^

error: aborting due to 2 previous errors