Add file missed in last commit; sched_lock() and sched_mergepending() now use sched_mergeprioritized()

Add library functions to concatenate and move lists.  Add scheduler function to merge prioritized function to merge prioritized lists (not yet used).

Fix issues detected by cppcheck

Remove most unused references to CONFIG_NET_MULTICAST.  Rename other uses of CONFIG_NET_MULTICAST to avoid naming comflicts.

TCP poll: TCP poll events can really only being processed when the poll from the correct device is received.

TCP timeouts: Fix some logic when there are multiple network  interfaces.  In this case, TCP timeout events can really only being processed when the poll from the correct device is received.