a cleanup of the receive_smb() usage, adding timeouts in some places

a cleanup of the receive_smb() usage, adding timeouts in some places

also added paranoid code in the main process() loop of smbd to detect
when smbd is looping uselessly. This should stop the "smbd is chewing
lots of cpu" reports
(This used to be commit 8e9dce34d50d673cb50531f0c4c7672ce2522cef)