Rename *last to *end

It is a more correct name because it points past the
last move of the list.

No functional change.

src/movepick.h

@@ -57,7 +57,7 @@ private:
   MoveStack killers[2];
   Square recaptureSquare;
   int captureThreshold, phase;
-  MoveStack *curMove, *lastMove, *lastQuiet, *lastBadCapture;
+  MoveStack *cur, *end, *endQuiets, *endBadCaptures;
   MoveStack moves[MAX_MOVES];
 };