codec/packet: move impl Send closer to the type definition

src/codec/packet/mod.rs

@@ -13,6 +13,8 @@ use ::{Error, format};
 
 pub struct Packet(AVPacket);
 
+unsafe impl Send for Packet { }
+
 impl Packet {
 	pub unsafe fn as_ptr(&self) -> *const AVPacket {
 		&self.0
@@ -131,8 +133,6 @@ impl Packet {
 	}
 }
 
-unsafe impl Send for Packet { }
-
 impl Clone for Packet {
 	fn clone(&self) -> Self {
 		let mut pkt = Packet::empty();