OS: Add a RUNNABLE attribute to the tasklists to indicate if the task list includes the currently executing task.  Use this additional bit of information to determine if a context switch could really occur when removing a TCB from a task list

Scheduler: Replace the boolean 'prioritized' with a uint8_t bit set so that additional attributes of a list can be specified without adding more boolean values.

DHCPD no longer calls directly into the OS, but uses network IOCTL commands to modify the ARP table.  Plus, fix a warning.

sched/: Replace explict references to g_readytorun with indirect references via the this_task() macro

syslog: If syslog timestamping is enabled, don't try to get the time if the timer hardware has not yet been initialized.

Add a state variable that provides the current level of OS initialization.  This is needed by some logic that may attempt to run early in the start-up sequence, but cannot run if a sufficient level of initializaitn has not not yet occurred