s3:smbd: SMB ReadX with size > 0xffff should only possible for samba clients.

s3:smbd: SMB ReadX with size > 0xffff should only possible for samba clients.

Windows 2008 R2 (and others) ignore the high bits for the read size.

Unless we're using the unix extentions and the client
uses CIFS_UNIX_LARGE_READ_CAP, we should also ignore
the high bits.

But we still need to support old "smbclient" binaries
and have to check if the client is "Samba".

metze

Signed-off-by: Jeremy Allison <jra@samba.org>