Support for contention logging with ART futexes.

Remove dangerous postfix operators on AtomicInteger. Clean up the atomic stack.
Factor nanosleep into a useful shared utils.h routine.

Change-Id: I417a73007c23fe247f410f41b2fa41a717c22139
diff --git a/src/utils.h b/src/utils.h
index 40f0768..640743c 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -291,6 +291,9 @@
 #define CLOCK_REALTIME 0xebadf00d
 #endif
 
+// Sleep for the given number of nanoseconds, a bad way to handle contention.
+void NanoSleep(uint64_t ns);
+
 // Initialize a timespec to either an absolute or relative time.
 void InitTimeSpec(bool absolute, int clock, int64_t ms, int32_t ns, timespec* ts);