message: Make Compiler::name() optional
  Makes the new Compiler::name() method optional by adding a default
  implementation.
  This avoid a breaking public API change.
diff: @@ -79,8 +79,11 @@ where
  /// An implementation of a Compiler from parsed WebAssembly module to Compiled native code.
  pub trait Compiler: Send {
  - /// Gets the name of this compiler
  - fn name(&self) -> &str;
  + /// Returns a descriptive name for this compiler.
  + // TODO!: Probably want to make this mandatory on the next major bump.
  + fn name(&self) -> &str {
  + "UNKNOWN"
  + }
  /// Validates a module.
  ///
  