Replace std::os::raw::c_ssize_t with std::os::raw::c_ptrdiff_t

Author: thomcc

library/std/src/os/raw/mod.rs

@@ -165,9 +165,9 @@ pub use core::ffi::c_void;
 #[unstable(feature = "c_size_t", issue = "88345")]
 pub type c_size_t = usize;
 
-/// Equivalent to C's `ssize_t` type, from `stddef.h` (or `cstddef` for C++).
+/// Equivalent to C's `ptrdiff_t` type, from `stddef.h` (or `cstddef` for C++).
 ///
 /// This type is currently always [`isize`], however in the future there may be
 /// platforms where this is not the case.
 #[unstable(feature = "c_size_t", issue = "88345")]
-pub type c_ssize_t = isize;
+pub type c_ptrdiff_t = isize;