Better naming in endgame code

And small clean-up of magic bitboards code.

No functional change.

Closes #1138

src/search.cpp

@@ -335,7 +335,7 @@ void Thread::search() {
   MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr);
 
   std::memset(ss-4, 0, 7 * sizeof(Stack));
-  for(int i = 4; i > 0; i--)
+  for (int i = 4; i > 0; i--)
      (ss-i)->history = &this->counterMoveHistory[NO_PIECE][0]; // Use as sentinel
 
   bestValue = delta = alpha = -VALUE_INFINITE;