Replace occurrences of "Mac OS X" with "macOS" in comments

Apple's main Operating system changed their name from OS X to macOS:

    https://www.engadget.com/2016/06/13/os-x-is-now-macos/

Revise source comments accordingly.

Source/QtDialog/CMakeSetupDialog.cxx

@@ -108,7 +108,7 @@ CMakeSetupDialog::CMakeSetupDialog()
 
   QMenu* ToolsMenu = this->menuBar()->addMenu(tr("&Tools"));
   this->ConfigureAction = ToolsMenu->addAction(tr("&Configure"));
-  // prevent merging with Preferences menu item on Mac OS X
+  // prevent merging with Preferences menu item on macOS
   this->ConfigureAction->setMenuRole(QAction::NoRole);
   QObject::connect(this->ConfigureAction, SIGNAL(triggered(bool)), this,
                    SLOT(doConfigure()));

Source/QtDialog/QCMakeCacheView.cxx

@@ -614,7 +614,7 @@ bool QCMakeCacheModelDelegate::editorEvent(QEvent* e,
 // Can remove this function and FileDialogFlag when minimum Qt version is 4.5
 bool QCMakeCacheModelDelegate::eventFilter(QObject* object, QEvent* evt)
 {
-  // workaround for what looks like a bug in Qt on Mac OS X
+  // workaround for what looks like a bug in Qt on macOS
   // where it doesn't create a QWidget wrapper for the native file dialog
   // so the Qt library ends up assuming the focus was lost to something else