message: Add crate version to debug output
diff: @@ -998,6 +998,7 @@ fn main() -> Result<()> {
  if features != 1 {
  panic!("Please select exactly one of the features: opencv-32, opencv-34, opencv-4");
  }
  + eprintln!("=== Crate version: {:?}", env::var_os("CARGO_PKG_VERSION"));
  eprintln!("=== Environment configuration:");
  for &v in ENV_VARS.iter() {
  eprintln!("=== {} = {:?}", v, env::var_os(v));
  