The big NULL replacement party part 1.

This is meant to be a safer alternative since
NULL can often be 0. Let's not rely on that.

And yes, I know this is a lot of files. This is
a safer thing to do in big commits vs for loops.

src/InputMapper.cpp

@@ -1111,7 +1111,7 @@ void InputMappings::WriteMappings( const InputScheme *pInputScheme, RString sFil
 	ini.DeleteKey( pInputScheme->m_szName );
 
 	XNode *pKey = ini.GetChild( pInputScheme->m_szName );
-	if( pKey != NULL )
+	if( pKey != nullptr )
 		ini.RemoveChild( pKey );
 	pKey = ini.AppendChild( pInputScheme->m_szName );