* win32/file.c (rb_file_expand_path_internal): Expand home directory when
used as second parameter (dir_string). [ruby-core:53168] [Bug #8034]
* test/ruby/test_file_exhaustive.rb: add test to verify.
* win32/file.c (get_user_from_path): add internal function that retrieves
username from supplied path (refactored).
* win32/file.c (rb_file_expand_path_internal): refactor expansion of user
home to use get_user_from_path and cover dir_string corner cases.
[ruby-core:53168] [Bug #8034]
merge revision(s) 39697,39701,39716,39740,39751: [Backport #8069]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@40249 b2dd03c8-39d4-4d8f-98ff-823fe69b080e