moved sync directory to root

sync/spinlock.hpp

@@ -0,0 +1,29 @@
+#ifndef MEMGRAPH_UTILS_SYNC_SPINLOCK_HPP
+#define MEMGRAPH_UTILS_SYNC_SPINLOCK_HPP
+
+#include <atomic>
+#include <unistd.h>
+
+class SpinLock
+{
+public:
+
+    void lock()
+    {
+        // TODO add asm pause and counter first before sleeping
+        // might be faster, but test this and see
+        while(lock_flag.test_and_set(std::memory_order_acquire))
+            usleep(250);
+    }
+
+    void unlock()
+    {
+        lock_flag.clear(std::memory_order_release);
+    }
+
+private:
+    // guaranteed by standard to be lock free!
+    std::atomic_flag lock_flag = ATOMIC_FLAG_INIT;
+};
+
+#endif