click: proc_dir missing from cvs repository; scheduled events in click; new serial link emulator element

[Eddie Kohler]

> 2. we expect to have many events scheduled, and a min_heap has faster random
> insertion time than than a linked list

Your code here will probably be valuable for Timer even if we don't take
over the whole event-scheduling framework.

> 3. we need to schedule events with finer granularity than 1ms; our scheduler
> attempts 1us granularity (well, that's too fine), and checks the timer
> between running threads.

Actually, Timer schedules down to nominally usec granularity. The ms
functions are there for convenience. Timer is also checked between running
threads, although it runs 32*128 threads between checking timers.

This area of Click definitely deserves attention and modification.

Eddie