string.c: scan coderange

* string.c (rb_str_conv_enc_opts): make sure to scan coderange to get
  rid of unnecessary conversion.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42998 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* enum.c: [DOC] Enumerable#to_a accepts arguments [GH-388]
  Patch by @kachick https://github.com/ruby/ruby/pull/388


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42999 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* enumerator.c: [DOC] Enumerator#each arguments documentation [GH-388]
  Patch by @kachick  https://github.com/ruby/ruby/pull/388


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43000 b2dd03c8-39d4-4d8f-98ff-823fe69b080e