scripted-diff: Use the C++11 keyword nullptr to denote the pointer literal instead of the macro NULL

-BEGIN VERIFY SCRIPT-
sed -i 's/\<NULL\>/nullptr/g' src/*.cpp src/*.h src/*/*.cpp src/*/*.h src/qt/*/*.cpp src/qt/*/*.h src/wallet/*/*.cpp src/wallet/*/*.h src/support/allocators/*.h
sed -i 's/Prefer nullptr, otherwise SAFECOOKIE./Prefer NULL, otherwise SAFECOOKIE./g' src/torcontrol.cpp
sed -i 's/tor: Using nullptr authentication/tor: Using NULL authentication/g' src/torcontrol.cpp
sed -i 's/METHODS=nullptr/METHODS=NULL/g' src/test/torcontrol_tests.cpp src/torcontrol.cpp
sed -i 's/nullptr certificates/NULL certificates/g' src/qt/paymentserver.cpp
sed -i 's/"nullptr"/"NULL"/g' src/torcontrol.cpp src/test/torcontrol_tests.cpp
-END VERIFY SCRIPT-

src/versionbits.h

@@ -27,7 +27,7 @@ enum ThresholdState {
 
 // A map that gives the state for blocks whose height is a multiple of Period().
 // The map is indexed by the block's parent, however, so all keys in the map
-// will either be NULL or a block with (height + 1) % Period() == 0.
+// will either be nullptr or a block with (height + 1) % Period() == 0.
 typedef std::map<const CBlockIndex*, ThresholdState> ThresholdConditionCache;
 
 struct VBDeploymentInfo {