* fhandler.h (fhandler_serial::is_tty): Reinstantiate.
	* fhandler.h (fhandler_serial::is_tty): Reinstantiate.
	* autoload.cc: Replace WNet[...]A with WNet[...]W imports.
	* dcrt0.cc (initial_env): Drop strlwr calls.  Call strcasestr instead.
	* fhandler_netdrive.cc: Throughout, convert to calling WNet UNICODE
	functions.  Use tmp_pathbuf rather than alloca.  Replace call to
	strlwr with call to RtlDowncaseUnicodeString.
	* fhandler.h (enum conn_state): Add "connect_credxchg" state.
	(class fhandler_socket): Grant another bit to connect_state flag.
	* fhandler_socket.cc (fhandler_socket::af_local_connect): Rearrange
	variable definition.  Set connect_state to connect_credxchg.
	(fhandler_socket::af_local_accept): Ditto.
	(fhandler_socket::recv_internal): Accept connect_credxchg on connection
	oriented AF_LOCAL sockets as well to allow the credential exchange.
	Extend comment to explain.
	* fhandler.h (enum conn_state): Add "connect_credxchg" state.
	(class fhandler_socket): Grant another bit to connect_state flag.
	* fhandler_socket.cc (fhandler_socket::af_local_connect): Rearrange
	variable definition.  Set connect_state to connect_credxchg.
	(fhandler_socket::af_local_accept): Ditto.
	(fhandler_socket::recv_internal): Accept connect_credxchg on connection
	oriented AF_LOCAL sockets as well to allow the credential exchange.
	Extend comment to explain.
	* fhandler.h (enum conn_state): Add "connect_credxchg" state.
	(class fhandler_socket): Grant another bit to connect_state flag.
	* fhandler_socket.cc (fhandler_socket::af_local_connect): Rearrange
	variable definition.  Set connect_state to connect_credxchg.
	(fhandler_socket::af_local_accept): Ditto.
	(fhandler_socket::recv_internal): Accept connect_credxchg on connection
	oriented AF_LOCAL sockets as well to allow the credential exchange.
	Extend comment to explain.
	* libc/machine/aarch64/memchr.S: Add check for zero-sized buffer.
	* dir.cc (dirfd): Per POSIX, return EINVAL on invalid directory stream.
	(telldir): Per POSIX, return -1 and set errno to EBADF, rather than
	just returning 0, on invalid directory stream.
	* signal.cc (sigwaitinfo): Return -1, not EFAULT, when SEGV was catched.
	* dir.cc (dirfd): Per POSIX, return EINVAL on invalid directory stream.
	(telldir): Per POSIX, return -1 and set errno to EBADF, rather than
	just returning 0, on invalid directory stream.
	* signal.cc (sigwaitinfo): Return -1, not EFAULT, when SEGV was catched.
	* dir.cc (dirfd): Per POSIX, return EINVAL on invalid directory stream.
	(telldir): Per POSIX, return -1 and set errno to EBADF, rather than
	just returning 0, on invalid directory stream.
	* signal.cc (sigwaitinfo): Return -1, not EFAULT, when SEGV was catched.