fuse: Use the high bit of request ID for indicating resend requests

Some FUSE daemons want to know if the received request is a resend
request. The high bit of the fuse request ID is utilized for indicating
this, enabling the receiver to perform appropriate handling.

The init flag "FUSE_HAS_RESEND" is added to indicate this feature.

Signed-off-by: Zhao Chen <winters.zc@antgroup.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>