Allow syscall::Result to accept other error types.

src/error.rs

@@ -5,7 +5,7 @@ pub struct Error {
     pub errno: i32,
 }
 
-pub type Result<T> = result::Result<T, Error>;
+pub type Result<T, E = Error> = result::Result<T, E>;
 
 impl Error {
     pub fn new(errno: i32) -> Error {