message: Use new delegate Button constructor in FileIo
diff: @@ -17,9 +17,9 @@ using namespace NAS2D;
  FileIo::FileIo() :
  Window{"File I/O"},
  - btnClose{"Cancel"},
  - btnFileOp{"FileOp"},
  - btnFileDelete{"Delete"}
  + btnClose{"Cancel", {this, &FileIo::onClose}},
  + btnFileOp{"FileOp", {this, &FileIo::onFileIo}},
  + btnFileDelete{"Delete", {this, &FileIo::onFileDelete}}
  {
  Utility<EventHandler>::get().mouseDoubleClick().connect(this, &FileIo::onDoubleClick);
  Utility<EventHandler>::get().keyDown().connect(this, &FileIo::onKeyDown);
  @@ -28,17 +28,14 @@ FileIo::FileIo() :
  add(btnFileOp, {445, 325});
  btnFileOp.size({50, 20});
  - btnFileOp.click().connect(this, &FileIo::onFileIo);
  btnFileOp.enabled(false);
  add(btnFileDelete, {5, 325});
  btnFileDelete.size({50, 20});
  - btnFileDelete.click().connect(this, &FileIo::onFileDelete);
  btnFileDelete.enabled(false);
  add(btnClose, {390, 325});
  btnClose.size({50, 20});
  - btnClose.click().connect(this, &FileIo::onClose);
  add(txtFileName, {5, 302});
  txtFileName.size({490, 18});
  