string.c: respect the actual encoding
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67167 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
string.c: respect the actual encoding
if a BOM presents, and scan for the actual code range.
[ruby-core:91662] [Bug #15635]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67167 b2dd03c8-39d4-4d8f-98ff-823fe69b080e