* array.c (ary_memcpy): add a function to copy VALUEs into ary
  with write barrier. If ary is promoted, use write barrier correctly.
* array.c (rb_ary_cat, rb_ary_unshift_m, rb_ary_dup,
  rb_ary_sort_bang, rb_ary_replace, rb_ary_plus): use ary_memcpy().



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42065 b2dd03c8-39d4-4d8f-98ff-823fe69b080e