parse.y: precedence of duplicated keys

* parse.y (assocs): concatenate splatted literal hashes.  the
  former key has precedence even if duplicated literal keys
  follow.  [ruby-core:65368] [Bug #10315]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47877 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
vm.c: precedence of duplicated keys

* vm.c (kwmerge_i): override existing keys by new keys.
  [ruby-core:65368] [Bug #10315]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47878 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
parse.y: remove duplicate keys

* parse.y (remove_duplicate_keys): remove duplicate literal keys,
  i.e., symbols and strings.  [ruby-core:65368] [Bug #10315]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47879 b2dd03c8-39d4-4d8f-98ff-823fe69b080e