Fix platform

- Add cfg to extern crate sc. It is not used by redox.
 - Fix bad syntax in brk implementation for redox
 - nits
   - style: update brk implementation for linux
   - style: no space between not operator and ptr.is_null
   - style: should be a space around = in module path

src/fcntl/src/lib.rs

@@ -9,11 +9,11 @@ use platform::types::*;
 pub use sys::*;
 
 #[cfg(target_os = "linux")]
-#[path="linux.rs"]
+#[path = "linux.rs"]
 pub mod sys;
 
 #[cfg(target_os = "redox")]
-#[path="redox.rs"]
+#[path = "redox.rs"]
 pub mod sys;
 
 pub const F_DUPFD: c_int = 0;