* test/ruby/test_file_exhaustive.rb
(TestFileExhaustive#test_stat_special_file): add a test.
GetFileAttributesExW fails to get attributes of special files
such as pagefile.sys.
* win32/win32.c (check_valid_dir): for performance, check the path
by FindFirstFileW only if the path contains "...".
* win32/win32.c (winnt_stat): use GetFileAttributesExW instead of
FindFirstFileW since GetFileAttributesExW is faster.
Based on the patch by Dusan D. Majkic.
[ruby-core:47083] [Feature #6845]
merge revision(s) 36668: [Backport #6846]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_3@36792 b2dd03c8-39d4-4d8f-98ff-823fe69b080e