gio: Add Send implementation to IOStreamAsyncReadWrite

This is a wrapper for GSocketConnection, which should be OK to share across
threads.

src/gio.rs

@@ -69,6 +69,8 @@ pub struct IOStreamAsyncReadWrite<T: IsA<gio::IOStream>> {
     write: gio::OutputStreamAsyncWrite<gio::PollableOutputStream>,
 }
 
+unsafe impl<T: IsA<gio::IOStream>> Send for IOStreamAsyncReadWrite<T> {}
+
 impl<T: IsA<gio::IOStream>> IOStreamAsyncReadWrite<T> {
     /// Create a new `gio::IOStream` adapter
     pub fn new(stream: T) -> Result<IOStreamAsyncReadWrite<T>, T> {

src/lib.rs

@@ -31,7 +31,6 @@
     unused_imports,
     unused_import_braces
 )]
-#![forbid(unsafe_code)]
 
 pub use tungstenite;