Auto merge of #2487 - rtzoeller:dfly_stat_deprecation, r=JohnTitor

Document stat.st_blksize changes on DragonFly BSD

The tests are currently failing on DragonFly BSD, due to [changes to `stat.st_blksize`](DragonFlyBSD/DragonFlyBSD@34c6728) among other reasons.

`st_blksize` is now an `i64`, and has moved to take up a previously reserved struct member. Deprecate the struct, to indicate it will be modified in a subsequent release.

Author: bors

src/unix/bsd/freebsdlike/dragonfly/mod.rs

@@ -106,6 +106,11 @@ s! {
         pub f_uid_uuid: ::uuid_t,
     }
 
+    #[deprecated(
+        since = "0.2.107",
+        note = "stat.st_blksize is an i64 and stat.st_qspare1 is replaced with \
+                stat.st_blksize in DragonFly 5.8"
+    )]
     pub struct stat {
         pub st_ino: ::ino_t,
         pub st_nlink: ::nlink_t,