merge revision(s) 42555: [Backport #8911]

	* hash.c (rb_hash_aset): [DOC] Document key dup patch by @kachick
	  [Fixes GH-382] https://github.com/ruby/ruby/pull/382


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@42945 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merge revision(s) 42890: [Backport #8878]

	* tool/rbinstall.rb (Gem::Specification#initialize): default date to
	  RUBY_RELEASE_DATE.  [ruby-core:57072] [Bug #8878]

	* tool/rbinstall.rb (Gem::Specification#to_ruby): add date.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@42946 b2dd03c8-39d4-4d8f-98ff-823fe69b080e