Revert automatically setting DTR when opening a port

This behavior looked promising in the first place to get some Arduino
devices to send data at all (like in #29 and #204). But after shipping
this as the new default, several issues were reported from other Arduino
devices and other places (see issue #243 and #251).

So I'm finally pulling the plug on this and revert setting DTR on open
by default. I'm sorry for the back and forth and all the inconvenience
this caused!

Author: sirhcel

src/lib.rs

@@ -859,11 +859,14 @@ pub fn new<'a>(path: impl Into<std::borrow::Cow<'a, str>>, baud_rate: u32) -> Se
         parity: Parity::None,
         stop_bits: StopBits::One,
         timeout: Duration::from_millis(0),
-        // By default, set DTR when opening the device. There are USB devices performing "wait for
-        // DTR" before sending any data and users stumbled over this multiple times (see issues #29
-        // and #204). We are expecting little to no negative consequences from setting DTR by
-        // default but less hassle for users.
-        dtr_on_open: Some(true),
+        // Leave DTR alone when opening a device. We've started out with setting DTR on open (see
+        // issues #29 and #204) but despite pleasing some Arduino use cases, this apparently caused
+        // problems with other boards and when using pseudo terminals (see issues #243 and #251).
+        //
+        // To me it looks that the fallout from setting DTR on open by default gets on a
+        // substantially larger area than the one benefitting from it, I finally decided to revert
+        // this. Sorry for this back and forth, Christian.
+        dtr_on_open: None,
     }
 }