Auto merge of #38648 - utkarshkukreti:question-mark-in-libstd-documentation-examples, r=pnkfelix,steveklabnik,frewsxcvx

libstd: replace all `try!` with `?` in documentation examples

See #38644.

For the record, I used the following Perl one-liner and then manually fixed a couple of things it got wrong:

    $ perl -p -i -e 's#(///.*)try!\((.*)\)#$1$2?#' src/libstd/**/*.rs

2 files changed, 4 insertions, 4 deletions

diff --git a/src/libstd/net/mod.rs b/src/libstd/net/mod.rs
index cadf87f32b1..2b60fc38198 100644
--- a/src/libstd/net/mod.rs
+++ b/src/libstd/net/mod.rs
@@ -129,7 +129,7 @@ impl fmt::Debug for LookupHost {
 /// use std::net;
 ///
 /// # fn foo() -> std::io::Result<()> {
-/// for host in try!(net::lookup_host("rust-lang.org")) {
+/// for host in net::lookup_host("rust-lang.org")? {
 ///     println!("found address: {}", host);
 /// }
 /// # Ok(())
diff --git a/src/libstd/net/udp.rs b/src/libstd/net/udp.rs
index a9a19aee5d1..492e57f6e44 100644
--- a/src/libstd/net/udp.rs
+++ b/src/libstd/net/udp.rs
@@ -28,16 +28,16 @@ use time::Duration;
 ///
 /// # fn foo() -> std::io::Result<()> {
 /// {
-///     let mut socket = try!(UdpSocket::bind("127.0.0.1:34254"));
+///     let mut socket = UdpSocket::bind("127.0.0.1:34254")?;
 ///
 ///     // read from the socket
 ///     let mut buf = [0; 10];
-///     let (amt, src) = try!(socket.recv_from(&mut buf));
+///     let (amt, src) = socket.recv_from(&mut buf)?;
 ///
 ///     // send a reply to the socket we received data from
 ///     let buf = &mut buf[..amt];
 ///     buf.reverse();
-///     try!(socket.send_to(buf, &src));
+///     socket.send_to(buf, &src)?;
 ///     # Ok(())
 /// } // the socket is closed here
 /// # }