Put back some C-style casts for now.

Change-Id: If95f524b10a4a6c346c7c2dc55b1c389a7c6cdd2
diff --git a/src/atomic.cc b/src/atomic.cc
index 0f4ff91..0625f1f 100644
--- a/src/atomic.cc
+++ b/src/atomic.cc
@@ -151,7 +151,7 @@
 #define SWAP_LOCK_COUNT  32U
 static pthread_mutex_t  _swap_locks[SWAP_LOCK_COUNT];
 
-#define SWAP_LOCK(addr) &_swap_locks[(reinterpret_cast<unsigned>(reinterpret_cast<void*>(addr)) >> 3U) % SWAP_LOCK_COUNT]
+#define SWAP_LOCK(addr) &_swap_locks[((unsigned)(void*)(addr) >> 3U) % SWAP_LOCK_COUNT]
 
 int64_t QuasiAtomicSwap64(int64_t value, volatile int64_t* addr) {
   pthread_mutex_t*  lock = SWAP_LOCK(addr);