Auto merge of #2364 - rtzoeller:dragonflybsd_fix_statfs, r=Amanieu

Fix statfs for DragonFlyBSD

The statfs struct was missing several padding areas and used incorrect array lengths, causing all values to be incorrect.

DragonFlyBSD's own documentation seems to be wrong here, which is likely how this ended up being incorrect in the first place.

Source: https://github.com/DragonFlyBSD/DragonFlyBSD/blob/27ea30e396c40d8feb44d76002b79153e96ecf8f/sys/sys/mount.h#L95
Documentation: https://man.dragonflybsd.org/?command=statfs&section=2

Author: bors

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

@@ -247,6 +247,7 @@ s_no_extra_traits! {
     }
 
     pub struct statfs {
+        __spare2: ::c_long,
         pub f_bsize: ::c_long,
         pub f_iosize: ::c_long,
         pub f_blocks: ::c_long,
@@ -256,15 +257,18 @@ s_no_extra_traits! {
         pub f_ffree: ::c_long,
         pub f_fsid: ::fsid_t,
         pub f_owner: ::uid_t,
-        pub f_type: i32,
-        pub f_flags: i32,
+        pub f_type: ::c_int,
+        pub f_flags: ::c_int,
         pub f_syncwrites: ::c_long,
         pub f_asyncwrites: ::c_long,
         pub f_fstypename: [::c_char; 16],
-        pub f_mntonname: [::c_char; 90],
+        pub f_mntonname: [::c_char; 80],
         pub f_syncreads: ::c_long,
         pub f_asyncreads: ::c_long,
-        pub f_mntfromname: [::c_char; 90],
+        __spares1: ::c_short,
+        pub f_mntfromname: [::c_char; 80],
+        __spares2: ::c_short,
+        __spare: [::c_long; 2],
     }
 
     pub struct sigevent {