rb_path_last_separator, rb_path_end, ruby_find_basename,
  ruby_find_extname): restore the declarations of these functions for
  backword compatibility.

* filc.c (rb_path_next, rb_path_skip_prefix, rb_path_last_separator,
  rb_path_end, ruby_find_basename, ruby_find_extname): implements
  these functions as the wrapper of rb_enc_*().


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_3@41878 b2dd03c8-39d4-4d8f-98ff-823fe69b080e