* path.cc (copy_cwd_str): Move up in file to be accessible from

	* path.cc (copy_cwd_str): Move up in file to be accessible from
	class fcwd_access_t.
	(class fcwd_access_t): New class to consolidate and hide the details
	of the various FAST_CWD implementations.  Add implementation for
	Windows 8 Developer Preview.
	(fast_cwd_version): Make static private member of fcwd_access_t.
	(fast_cwd_ptr): Change base type to fcwd_access_t.
	(find_fast_cwd_pointer): Return fcwd_access_t**.
	(find_fast_cwd): Ditto.  Rip out all FAST_CWD implementations and use
	fcwd_access_t methods instead.
	(cwdstuff::override_win32_cwd): Ditto.