Core: Remove deprecated accessors

Also adjust user code.

Change-Id: I60935942a7012e6a0d6091ffbc89d69289366e35
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/coreplugin/icore.cpp

@@ -407,41 +407,16 @@ bool ICore::showWarningWithOptions(const QString &title, const QString &text,
                                                 settingsId, parent);
 }
 
-ActionManager *ICore::actionManager()
-{
-    return m_mainwindow->actionManager();
-}
-
-DocumentManager *ICore::documentManager()
-{
-    return DocumentManager::instance();
-}
-
-MessageManager *ICore::messageManager()
-{
-    return m_mainwindow->messageManager();
-}
-
 ProgressManager *ICore::progressManager()
 {
     return m_mainwindow->progressManager();
 }
 
-VariableManager *ICore::variableManager()
-{
-    return m_mainwindow->variableManager();
-}
-
 VcsManager *ICore::vcsManager()
 {
     return m_mainwindow->vcsManager();
 }
 
-ModeManager *ICore::modeManager()
-{
-    return m_mainwindow->modeManager();
-}
-
 MimeDatabase *ICore::mimeDatabase()
 {
     return m_mainwindow->mimeDatabase();