examples: Use tracing macros instead of println!

This allows the examples to work a bit better in WASM and on iOS.

winit-x11/src/util/mod.rs

@@ -66,7 +66,6 @@ impl XConnection {
     // All util functions that abstract an async function will return a `Flusher`.
     pub fn flush_requests(&self) -> Result<(), XError> {
         unsafe { (self.xlib.XFlush)(self.display) };
-        // println!("XFlush");
         // This isn't necessarily a useful time to check for errors (since our request hasn't
         // necessarily been processed yet)
         self.check_errors()
@@ -74,7 +73,6 @@ impl XConnection {
 
     pub fn sync_with_server(&self) -> Result<(), XError> {
         unsafe { (self.xlib.XSync)(self.display, ffi::False) };
-        // println!("XSync");
         self.check_errors()
     }
 }