Add comment about TIOCGWINSZ .into().

Author: ehuss

src/cargo/core/shell.rs

@@ -377,6 +377,8 @@ mod imp {
     pub fn stderr_width() -> Option<usize> {
         unsafe {
             let mut winsize: libc::winsize = mem::zeroed();
+            // The .into() here is needed for FreeBSD which defines TIOCGWINSZ
+            // as c_uint but ioctl wants c_ulong.
             if libc::ioctl(libc::STDERR_FILENO, libc::TIOCGWINSZ.into(), &mut winsize) < 0 {
                 return None;
             }