Ruby

• gc.c: fix a regression by r31690 on AIX because AIX malloc
  return NULL if it's passed 0. But some caller don't expect it.
  patch by Yutaka Kanemoto.
  (vm_malloc_prepare): return calculated size.
  (vm_xmalloc): use above result.
  (vm_xcalloc): ditto.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@32103 b2dd03c8-39d4-4d8f-98ff-823fe69b080e