[PrefsManager] Add StretchBackgrounds preference.

src/PrefsManager.cpp

@@ -172,6 +172,7 @@ PrefsManager::PrefsManager() :
 	m_iDisplayColorDepth	( "DisplayColorDepth",		16 ),
 	m_iTextureColorDepth	( "TextureColorDepth",		16 ),
 	m_iMovieColorDepth	( "MovieColorDepth",		16 ),
+	m_bStretchBackgrounds	( "StretchBackgrounds",		false ),
 	m_HighResolutionTextures	( "HighResolutionTextures",	HighResolutionTextures_Auto ),
 	m_iMaxTextureResolution	( "MaxTextureResolution",	2048 ),
 	m_iRefreshRate		( "RefreshRate",		REFRESH_DEFAULT ),

src/PrefsManager.h

@@ -163,6 +163,7 @@ public:
 	Preference<int>	m_iDisplayColorDepth;
 	Preference<int>	m_iTextureColorDepth;
 	Preference<int>	m_iMovieColorDepth;
+	Preference<bool>	m_bStretchBackgrounds;
 	Preference<HighResolutionTextures>	m_HighResolutionTextures;
 	Preference<int>	m_iMaxTextureResolution;
 	Preference<int>	m_iRefreshRate;

src/ScreenOptionsMasterPrefs.cpp

@@ -687,6 +687,7 @@ static void InitializeConfOptions()
 	g_ConfOptions.back().m_sPrefName = "BGBrightness";
 	ADD( ConfOption( "BGBrightnessOrStatic",	BGBrightnessOrStatic,	"Disabled","25% Bright","50% Bright","75% Bright" ) );
 	g_ConfOptions.back().m_sPrefName = "BGBrightness";
+	ADD( ConfOption( "StretchBackgrounds",			MovePref<bool>,		"Off","On" ) );
 
 	ADD( ConfOption( "ShowDanger",			MovePref<bool>,		"Hide","Show" ) );
 	ADD( ConfOption( "ShowDancingCharacters",	MovePref<ShowDancingCharacters>, "Default to Off","Default to Random","Select" ) );