got rid of all uses of strerror

This required some minor refactoring of other things and there were some
other small cleanups I noticed along the way.
diff --git a/aos/common/queue_testutils.cc b/aos/common/queue_testutils.cc
index 1b9b731..ed89d4f 100644
--- a/aos/common/queue_testutils.cc
+++ b/aos/common/queue_testutils.cc
@@ -128,7 +128,7 @@
                       MAP_SHARED | MAP_ANONYMOUS, -1, 0);
   assert(memory != MAP_FAILED);
 
-  assert(aos_core_use_address_as_shared_mem(memory, kCoreSize) == 0);
+  aos_core_use_address_as_shared_mem(memory, kCoreSize);
 
   EnableTestLogging();
 }