move to <limits.h> where possible, annotate <sys/param.h> otherwise

Change the error handling a bit to ensure we do not double free the task
by calling conn_task_cleanup() twice (once direct and once via conn_fail()).
The error handling needs some more work but at least this fixes the crash
found by jasper@

Extend the connection and session FSMs so that connection failure is
handled more gracefully. Losing the TCP connection no longer results
in an unrecoverable stop requiring a restart of iscsid.

Fix conn_gen_kvp and its caller to fill the kvp array properly (including
the NULL terminator at the end). Now iscsid does proper LoginOperational
negotiation (which will bump the MaxRecvDataSegmentLength to 64k)

COnveret the bcopy() to memcpy()

Replace a magic number.

Massive diff to handle logins more correctly. iscsid will now do
better operational parameter negotiation but more is needed.
Tested by todd@ and myself.

Rework the logout code and use this to do a proper logout when
exiting. This works well for idle sessions but still has some
issues on busy session. It seems more task scheduler changes are
needed to make this work. This also includes some mem-leak fixes
in error pathes found by Igor Zinovik.
go for it dlg@

Rename task_cleanup() to conn_task_cleanup() seems a better place for
this function since it does connections scheduling.

Start implementing the FSM. Introduce a session FSM that is run via a
callback and implement some of the connection FSM actions. Implement
logouts so that discovery sessions do a nice login -> query -> logout.
Fix the task scheduling especially for immediate and connection specific
tasks. The session will now only schedule tasks to a session that is
in LOGGED_IN state.
looks good dlg@

Move session related code into session.c.

Implememnt NOP-IN -> NOP-OUT handling. If the NOP-In was issued by the
target (itt = 0xffffffff) send back an immediate NOP-Out reusing the
NOP-In PDU. This makes my iscsi target happy.
Also plug a mem leak on error path which was found by Igor Zinovik.

spacing, no binary changes.

fix typos in documentation and log_debug() function.

ok claudio@

iSCSI Initiatior daemon using vscsi(4).
Currently implements the absolute minimum of the protocol to make
it work against targets. Many things still in flux but we're annoyed
to work outside of the tree. Commited from a source tree on an iSCSI
disk served via iscsid but it is not yet production ready.
OK dlg@, matthew@, deraadt@