add FIXME related to the -fno-strict-aliasing workaround

Author: marijnh

src/rt/sync/lock_free_queue.h

@@ -88,6 +88,8 @@ class lock_free_queue {
         pointer_t *oldValue,
         pointer_t newValue) {
 
+        // FIXME this is requiring us to pass -fno-strict-aliasing to GCC
+        // (possibly there are other, similar problems)
         if (sync::compare_and_swap(
                 (uint64_t*) address,
                 *(uint64_t*) oldValue,