More gc-friendly property hashmap allocation.

- New allocator is added that returns null on out of memory, property hasmap create uses this allocator for now.
- Property hashmaps of objects are removed durring a high severity gc.

Follow up patch is in progress.

JerryScript-DCO-1.0-Signed-off-by: István Kádár ikadar@inf.u-szeged.hu

jerry-core/ecma/base/ecma-init-finalize.c

@@ -54,7 +54,7 @@ ecma_finalize (void)
 
   ecma_finalize_environment ();
   ecma_finalize_builtins ();
-  ecma_gc_run ();
+  ecma_gc_run (JMEM_FREE_UNUSED_MEMORY_SEVERITY_LOW);
   ecma_finalize_lit_storage ();
 } /* ecma_finalize */