Update Stream.cpp

teensy3/Stream.cpp

 // as find but search ends if the terminator string is found
 bool  Stream::findUntil(const char *target, const char *terminator)
 {
-  if(target == NULL) return true;
-  size_t tlen = (terminator==NULL)?0:strlen(terminator);
+  if(target == nullptr) return true;
+  size_t tlen = (terminator==nullptr)?0:strlen(terminator);
   return findUntil(target, strlen(target), terminator, strlen(terminator));
 }
 
   size_t index = 0;  // maximum target string length is 64k bytes!
   size_t termIndex = 0;
   int c;
-  if( target == NULL) return true;
+  if( target == nullptr) return true;
   if( *target == 0) return true;   // return true if target is a null string
-  if (terminator == NULL) termLen = 0;
+  if (terminator == nullptr) termLen = 0;
 
   while( (c = timedRead()) > 0){
     if( c == target[index]){