Fix arenas_cache_cleanup() and arena_get_hard().

Fix arenas_cache_cleanup() and arena_get_hard() to handle
allocation/deallocation within the application's thread-specific data
cleanup functions even after arenas_cache is torn down.

This is a more general fix that complements
45e9f66c280e1ba8bebf7bed387a43bc9e45536d (Fix arenas_cache_cleanup().).
diff --git a/ChangeLog b/ChangeLog
index 97728b0..17f6538 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -7,9 +7,9 @@
 * 4.0.1 (XXX)
 
   Bug fixes:
-  - Fix arenas_cache_cleanup() to handle allocation/deallocation within the
-    application's thread-specific data cleanup functions even after
-    arenas_cache is torn down.
+  - Fix arenas_cache_cleanup() and arena_get_hard() to handle
+    allocation/deallocation within the application's thread-specific data
+    cleanup functions even after arenas_cache is torn down.
   - Don't bitshift by negative amounts when encoding/decoding run sizes in chunk
     header maps.  This affected systems with page sizes greater than 8 KiB.
   - Rename index_t to szind_t to avoid an existing type on Solaris.