Remove CStereoscopicsManager instance

The first step in killing globals is to identify if the service is
instantiated as a global or singleton. In this case, the service is a
singleton. Remove this instance.

Singletons usually have private constructors. Make all constructors public.

Author: garbear

xbmc/guilib/StereoscopicsManager.cpp

@@ -106,12 +106,6 @@ CStereoscopicsManager::CStereoscopicsManager(void)
 
 CStereoscopicsManager::~CStereoscopicsManager(void) = default;
 
-CStereoscopicsManager& CStereoscopicsManager::GetInstance()
-{
-  static CStereoscopicsManager sStereoscopicsManager;
-  return sStereoscopicsManager;
-}
-
 void CStereoscopicsManager::Initialize(void)
 {
   // turn off stereo mode on XBMC startup

xbmc/guilib/StereoscopicsManager.h

@@ -48,11 +48,6 @@ class CStereoscopicsManager : public ISettingCallback,
   CStereoscopicsManager(void);
   ~CStereoscopicsManager(void) override;
 
-  /*!
-   * @return static instance of CStereoscopicsManager
-   */
-  static CStereoscopicsManager& GetInstance();
-
   void Initialize(void);
   RENDER_STEREO_MODE GetStereoMode(void);
   void SetStereoModeByUser(const RENDER_STEREO_MODE &mode);