Reintroduce Copy and Clone traits for ReadFlag (#116)

The traits were removed unintentionally when bitflag was
updated to v2 as part of 0.6.2 release. The v2 removes
the automatic derivation of certain traits. I'm putting
back all the traits that were removed in order to not
break any code that relied on it.

Signed-off-by: Nayan Deshmukh <[email protected]>

Author: ndesh26

src/lib.rs

@@ -89,6 +89,7 @@ pub enum GrabMode {
 }
 
 bitflags! {
+#[derive(PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Clone, Copy)]
     pub struct ReadFlag: u32 {
         /// Process data in sync mode
         const SYNC = 1;