re.c: mak eregexps with binary escapes ASCII-8BIT

* re.c (unescape_nonascii): make dynamically compiled US-ASCII
  regexps ASCII-8BIT encoding if binary (hexadecimal, control,
  meta) escapes are contained, as well as literal regexps.
  [ruby-dev:48626] [Bug #10382]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47992 b2dd03c8-39d4-4d8f-98ff-823fe69b080e