clang-modernize -use-nullptr

and s/\bNULL\b/nullptr/g for *.cpp/h/mm files not compiled on my machine

Source/Core/VideoBackends/Software/SWmain.cpp

@@ -60,7 +60,7 @@ std::string VideoSoftware::GetName()
 
 void *DllDebugger(void *_hParent, bool Show)
 {
-	return NULL;
+	return nullptr;
 }
 
 void VideoSoftware::ShowConfig(void *_hParent)