make statfs/statvfs to be available everywhere

libc reads sys/statvfs.h on all OS except Windows which nix doesn't care
about.

Closes: #831
Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>

src/sys/mod.rs

@@ -62,20 +62,7 @@ pub mod select;
 #[cfg(target_os = "linux")]
 pub mod quota;
 
-
-#[cfg(all(target_os = "linux",
-          any(target_arch = "x86",
-              target_arch = "x86_64",
-              target_arch = "arm")),
-          )]
 pub mod statfs;
-
-
-#[cfg(all(any(target_os = "linux",
-              target_os = "macos"),
-          any(target_arch = "x86",
-              target_arch = "x86_64",
-              target_arch = "arm")),
-          )]
 pub mod statvfs;
+
 pub mod pthread;