* array.c (ary_mem_clear): added. This operation doesn't need WB
  because this operation creates a reference to Qnil.
* array.c (ary_make_shared, rb_ary_store, rb_ary_shift_m,
  rb_ary_splice, rb_ary_resize, rb_ary_fill): use ary_mem_clear()
  instead of rb_mem_clear().
* array.c (ary_make_shared): use RARRAY_RAWPTR() instead of RARRAY_PTR().



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42070 b2dd03c8-39d4-4d8f-98ff-823fe69b080e