Use new atomis with allocated_heap.

mono/metadata/sgen-memory-governor.c

@@ -72,8 +72,7 @@ sgen_memgov_adjust_allowance (mword allowance_estimate, mword new_heap_size)
 void
 sgen_memgov_release_space (mword size, int space)
 {
-	/*FIXME CAS*/
-	allocated_heap -= size;
+	SGEN_ATOMIC_ADD_P (allocated_heap, -size);
 }
 
 gboolean
@@ -82,8 +81,7 @@ sgen_memgov_try_alloc_space (mword size, int space)
 	if (sgen_memgov_available_free_space () < size)
 		return FALSE;
 
-	/*FIXME CAS*/
-	allocated_heap += size;
+	SGEN_ATOMIC_ADD_P (allocated_heap, size);
 	mono_runtime_resource_check_limit (MONO_RESOURCE_GC_HEAP, allocated_heap);
 	return TRUE;
 }