Use question_mark feature in libstd.

Author: ahmedcharles

src/libstd/sync/mpsc/oneshot.rs

@@ -150,7 +150,7 @@ impl<T> Packet<T> {
                     let timed_out = !wait_token.wait_max_until(deadline);
                     // Try to reset the state
                     if timed_out {
-                        try!(self.abort_selection().map_err(Upgraded));
+                        self.abort_selection().map_err(Upgraded)?;
                     }
                 } else {
                     wait_token.wait();

src/libstd/sync/mpsc/stream.rs

@@ -187,8 +187,7 @@ impl<T> Packet<T> {
             if let Some(deadline) = deadline {
                 let timed_out = !wait_token.wait_max_until(deadline);
                 if timed_out {
-                    try!(self.abort_selection(/* was_upgrade = */ false)
-                             .map_err(Upgraded));
+                    self.abort_selection(/* was_upgrade = */ false).map_err(Upgraded)?;
                 }
             } else {
                 wait_token.wait();

src/libstd/sys/common/backtrace.rs

@@ -153,11 +153,11 @@ pub fn demangle(writer: &mut Write, s: &str) -> io::Result<()> {
                     macro_rules! demangle {
                         ($($pat:expr => $demangled:expr),*) => ({
                             $(if rest.starts_with($pat) {
-                                try!(writer.write_all($demangled));
+                                writer.write_all($demangled)?;
                                 rest = &rest[$pat.len()..];
                               } else)*
                             {
-                                try!(writer.write_all(rest.as_bytes()));
+                                writer.write_all(rest.as_bytes())?;
                                 break;
                             }