Ignore buggy clippy::incompatible_msrv lint

rust-lang/rust-clippy#12280

```
error: current MSRV (Minimum Supported Rust Version) is `1.36.0` but this item is stable since `1.37.0`
   --> src/lib.rs:224:20
    |
224 |     let buffer = v.as_mut_ptr();
    |                    ^^^^^^^^^^^^
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#incompatible_msrv
    = note: `-D clippy::incompatible-msrv` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::incompatible_msrv)]`
```

src/lib.rs

@@ -215,6 +215,7 @@ macro_rules! ready {
 /// # Panics
 ///
 /// This function panics if `cap` is 0 or if `cap * 2` overflows a `usize`.
+#[allow(clippy::incompatible_msrv)] // false positive: https://github.com/rust-lang/rust-clippy/issues/12280
 pub fn pipe(cap: usize) -> (Reader, Writer) {
     assert!(cap > 0, "capacity must be positive");
     assert!(cap.checked_mul(2).is_some(), "capacity is too large");