* win32/win32.c (fileattr_to_unixmode, rb_w32_reparse_symlink_p): volume
	  mount point should be treated as directory, not symlink.
	  [ruby-core:72483] [Bug #11874]

	* win32/win32.c (rb_w32_read_reparse_point): check the reparse point is
	  a volume mount point or not.

	* win32/file.c (rb_readlink): follow above change (but this pass won't
	  be used).

	* win32/file.c (rb_readlink): drop garbage after the substitute
	  name, as rb_w32_read_reparse_point returns the expected buffer
	  size but "\??\" prefix is dropped from the result.

	* win32/win32.c (w32_readlink): ditto, including NUL-terminator.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@54424 b2dd03c8-39d4-4d8f-98ff-823fe69b080e