clang-modernize -use-nullptr

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

Source/Core/VideoBackends/Software/BPMemLoader.cpp

@@ -100,7 +100,7 @@ void SWBPWritten(int address, int newvalue)
 			u32 tlutTMemAddr = (newvalue & 0x3FF) << 9;
 			u32 tlutXferCount = (newvalue & 0x1FFC00) >> 5;
 
-			u8 *ptr = 0;
+			u8 *ptr = nullptr;
 
 			// TODO - figure out a cleaner way.
 			if (Core::g_CoreStartupParameter.bWii)