merge revision(s) r47591: [Backport #10242]

	* ext/pathname/lib/pathname.rb (SAME_PATHS):
	  Pathname#relative_path_from uses String#casecmp to compare strings
	  on case-insensitive filesystem platforms (e.g., Windows). This can
	  return nil for strings with different encodings, and the code
	  previously assumed that it always returned a Fixnum.  [Fix GH-713]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@47596 b2dd03c8-39d4-4d8f-98ff-823fe69b080e