Implement frame dumping in D3D11.

Fixes issue 4831.

Source/Core/VideoCommon/Src/RenderBase.cpp

@@ -52,7 +52,7 @@ int OSDChoice, OSDTime;
 
 Renderer *g_renderer = NULL;
 
-bool s_bLastFrameDumped = false;
+bool bLastFrameDumped = false;
 std::mutex Renderer::s_criticalScreenshot;
 std::string Renderer::s_sScreenshotName;
 

Source/Core/VideoCommon/Src/RenderBase.h

@@ -41,7 +41,7 @@
 extern int frameCount;
 extern int OSDChoice, OSDTime;
 
-extern bool s_bLastFrameDumped;
+extern bool bLastFrameDumped;
 
 // Renderer really isn't a very good name for this class - it's more like "Misc".
 // The long term goal is to get rid of this class and replace it with others that make