* array.c (ARY_SET): added.
  ARY_SET() is same functionality of RARRAY_ASET(), but
  it has an assertion (`ary' doesn't have shared array).



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45569 b2dd03c8-39d4-4d8f-98ff-823fe69b080e