artf4107: clang-modernize was run on WPILib

Loops were converted to their range-based equivalents, variable types were replaced with auto where the type was already specified on the same line, the override keyword was added, and instances of NULL and assignments of 0 to pointers were replaced with nullptr.

Change-Id: If281e46a2e2e1c37f278d56df9915236d4b2c864

wpilibc/wpilibC++Sim/include/simulation/MainNode.h

@@ -10,7 +10,7 @@ using namespace gazebo;
 class MainNode {
 public:
 	static MainNode* GetInstance() {
-		if (instance == NULL) {
+		if (instance == nullptr) {
 			instance = new MainNode();
 		}
 		return instance;