[ruby-cvs:78836] 204dc3f39f (master): Revert "Should return "." for File.extname("file.") also on Windows"

NAKAMURA Usaku	2019-12-23 11:54:25 +0900 (Mon, 23 Dec 2019)

  New Revision: 204dc3f39f

  https://github.com/ruby/ruby/commit/204dc3f39f

  Log:
    Revert "Should return "." for File.extname("file.") also on Windows"
    
    We want to introduce consistency and better compatibility with unixen,
    but the Windows APIs doues not have consistency fundamentally and
    we can not found any logical way...
    
    This reverts commit 61aff0cd189e67fa6f2565639ad0128fa33b88fc.

  Modified files:
    file.c
    spec/ruby/core/file/extname_spec.rb
    test/ruby/test_file_exhaustive.rb
    test/ruby/test_path.rb